Doctoral Degrees (Animal and Poultry Science)

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Characterisation of indigenous Zulu (Nguni) sheep for utilisation improvement and conservation.
(2010) Kunene, Nokuthula Winfred.; Nsahlai, Ignatius Verla.; Bezuidenhout, Carel Nicolaas.; Nesamvuni, A. E.
The Nguni sheep of Zululand, South Africa, are called the Zulu sheep. They are a source of food and cash for the rural farmers of KwaZulu-Natal. There is insufficient information available about the characteristics of this breed and accordingly the breed is classified as “insecure”. Documentation of characteristics of a breed is important for its utilisation, improvement or conservation. This study was undertaken to document (i) the utilization of the Zulu sheep, (ii) some morphological characteristics, (iii) establishing a cost effective body measurement recording means and (iv) the intra- and inter-population genetic variation of the breed using random amplified polymorphic DNA markers. A survey was conducted to investigate the socio-economic and cultural values of the farmers attached to livestock including the Zulu sheep. A total of 76 rural farmers were interviewed in the areas of the Mhlathuze district in northern KwaZulu-Natal. Constraints and the indigenous knowledge of the farmers on livestock production were also recorded. The results confirmed that the Zulu sheep in the rural areas are indeed used as a source of protein and cash when necessary. Farmers reported that the Zulu sheep are tolerant to ticks and able to withstand the hot and humid conditions of northern KwaZulu-Natal. Goats and cattle as well as the Zulu sheep are also used for payment of dues in the tribal courts. Even so, Zulu sheep are not used for any cultural purposes. The system of management is fairly extensive. Some farmers apply indigenous knowledge as part of management practices. For instance, they use indigenous plants as nutrient supplements and for increasing the reproduction rate of these animals. Lack of modern animal husbandry skills was declared by the farmers as one of the main challenges. A perception among the farmers was that the Government could assist in addressing this challenge. Three populations of Zulu sheep reared extensively in three localities were used for the morphometric and genetic studies. The areas were the community of KwaMthethwa (Enqutshini), University of Zululand (UNIZULU) and Makhathini Research Station. Makhathini and KwaMthethwa are 260 and 40 km, respectively, away from UNIZULU. The morphometric study was undertaken to determine the extent of phenotypic diversity between Zulu sheep populations using six morphological characteristics. Effects of some factors (location, age, sex and season) on some of these traits were estimated. Results showed that the size of the body measurements, wither height (WH), heart girth (HG), live weight (LW) and scrotal circumference (SC) were significantly different between the populations. Variation in these body measurements was influenced significantly by the location, season, the sex and the age of sheep. Mature ewes weighed up to 32 kg whereas the rams weighed up to 38 kg. The differences in LW, HG and WH between the seasons were small. The SC increased with the age of the ram up to 28 cm for mature rams. Other traits observed were the colour and the ear length of Zulu sheep. Ear size ranged from ear buds to the most common large ears (9 to 14 cm). The dominating colours observed were brown and a combination of brown and white. Live weight prediction equations were estimated employing HG, WH and SC data. The LW prediction equations showed that the regression of HG and WH produce the best estimate equations of LW; however the HG alone also showed reliable LW estimates. Scrotal circumference was more precise for estimating the LW of younger rams below 22 months of age (R2 = 0.64 – 0.78). Fifty-two Zulu sheep from the three locations were used to assess the genetic variation within the Zulu sheep breed. A total of 2744 RAPD bands were generated ranging from 0.2 to 2 kb; ~46% of these bands were polymorphic. The genetic diversity was the lowest (5.17%) within the UNIZULU population, 8.62% within the KwaMthethwa population and highest (11.04%) within the Makhathini population. The genetic diversity between all populations was estimated at 21.91 %. Phenotypic diversity was relatively similar for the UNIZULU and Makhathini populations (41.25% and 45.63%, respectively). The phenotypic diversity between the three populations was 48.26%. Genetic and phenotypic diversity was lower for Makhathini and UNIZULU populations than for the KwaMthethwa population. It was concluded that the Zulu sheep is a smaller sized breed compared to the other South African indigenous sheep breeds like the Dorper which has been reported to have some similar characteristics to the Nguni sheep. The results confirmed that the Zulu breed has the capacity to survive without dipping and supplements during the dry season. This adaptation is of value to the communities of KwaZulu-Natal. Such characteristics warrant conserving the breed to prevent genetic erosion. The phenotypic and genetic diversity between the three populations of Zulu sheep may indicate that there is an opportunity of genetic exploitation by selecting animals based on phenotypic as well as genetic characteristics. In order to promote the conservation and sustainable use of the Zulu sheep, it was recommended that an open nucleus breeding scheme from lower-tier flocks (of the farmers) for pure breeding to nucleus flocks (in Government ranches) could be appropriate. The scheme would also address the challenges of animal husbandry as well as contribute to the improvement of the livelihood of the farmers. Farmers could use a tape measure to estimate the LW of sheep when they cannot afford scales. The morphological characteristics and the genetic diversity data generated from this study could be combined into a single data base for this sheep breed. More extensive studies, using the same or some additional phenotypic characters such as reproductive performance, need to be done. Genetic characteristics of Zulu sheep using microsatellites and mitochondrial DNA should be done to complement the present study.
Modelling broiler populations for purposes of optimisation.
(2008) Berhe, Esayas Tesfasellassie.; Gous, Robert Mervyn.
With the narrow margin of profit in the broiler enterprise, how can producers increase profit potential? It is not an easy task to answer this question since the net financial return depends on many factors; some are related to the animal, some to the feed, some to the environment and others are outside the production system, like availability and cost of labour and capital. Many researchers have attempted to improve the efficiency of the system using alternative management strategies and to develop a unified theory that could simultaneously evaluate all the relevant factors and the interactions between them. Simulation models are seen as the most promising means of moving this subject forward. Geneticists are continually improving the potential growth rate of broilers, yet there has been little change in feed specifications for these birds over the past few decades. Only recently has it been possible to make use of simulation models to optimise the feeds and feeding programs of modern broiler strains at a commercial level, but little testing of these programs has been carried out. What is needed is a thorough investigation of these models, which at present are based on an individual, as opposed to a population response. Modelling plays an increasingly important part in animal science and research as a way of organizing and evaluating the large body of existing knowledge. With the use of an accurate description of the potential growth rates of broiler genotypes, it is possible to make more efficient use of growth models which are becoming more abundant in the industry and which, in turn, enable the nutritionist or producer to predict the performance of animals when subjected to a given feed or feeding programme. The predictions made by most of the growth models now available are based on individual animals, and the results obtained may be inadequate in optimising the nutrient requirements of a broiler population because of the variation that exists in these populations. Variation in performance traits in broilers may be the result of variation in the genotype, in the environmental conditions within the house, and in the composition of the feed offered to the birds, and these sources of variation cannot all be accommodated in a model that simulates the food intake and growth of just one bird. But if variation is to be incorporated into growth models, it is necessary to ascertain the effects of variation in the various genetic parameters on the mean response of the population. A sensitivity analysis is useful in accomplishing this objective. Similarly, it is important to know what the optimum size of a simulated population should be, that takes account both of the accuracy of the simulation and the time taken to complete the exercise. This is especially important when optimisation routines are followed, as such calculations are time consuming. As a means of addressing these issues, simulation exercises were conducted using EFG Broiler Growth Model version 6 and EFG Broiler Optimiser Model version 1 (EFG Software, 2006) to determine: (a) whether it is worth generating a population when optimising feeds and feeding programs for broilers, rather than using the average individual, (b) the size of the population required to obtain an accurate estimate of the population response when optimising the feeding program for different objective functions, (c) the effect of changing the value of genetic parameters such as mature protein weight, rate of maturing, feathering rate and the maximum lipid:protein ratio in the gain on the optimum amino acid contents and nutrient densities of broiler feeds, and (d) the effect of variation in nutrient composition of different batches of feed, which have the same nutrient profile but different qualities of the main protein source, on broiler performance. A review of sources of variation in the nutrient content of poultry feed was conducted, and simulation exercises were carried out to determine to what extent broiler performance is affected by the segregation or breakage of pellets into small pieces at the time of delivery and along the feed conveyor within the broiler house, by the change in nutrient quality that might occur along the conveyor, and by the microclimates that develop in a longitudinally ventilated broiler house. The tendency in broiler marketing in most parts of the world is to sell broilers cut up, as portions or deboned after evisceration, rather than selling whole birds. Estimation of the growth rates of carcass parts is therefore of considerable importance if simulation models are to be useful in optimising the feeds and feeding programmes of broilers under different conditions. Allometric equations are used in the EFG broiler growth model to predict the weights of these carcass parts from the weight of body protein at the time. These equations are based on data collected many years ago, and it would be useful to determine whether they are still relevant in the face of announcements by the major broiler breeding companies that tremendous strides have been made in improving breast meat yield, for example, by judicious selection. For the purpose of this investigation it was important to determine to what extent the weights of the physical parts varied at the same body protein weight, thereby enabling a more accurate estimation of the variation that could be expected in these weights when developing a population response model. Towards this end, experiments were conducted to determine the effect of dietary protein content on the performance of Cobb and Ross broilers, including mortality and uniformity, and on the allometric relationships between the physical and chemical components of the body and body protein. The overall objective of these exercises was to address issues relating to the use of simulation models in predicting food intake and growth of broilers, in optimising the amino acid contents and nutrient densities of feeds for broilers, and in representing a population of broilers when the performance of only one bird is simulated at a time.
The photoperiodic response of male broiler breeders.
(2010) Tyler, Nicola Claire.; Gous, Robert Mervyn.
The expression of photorefractoriness, a feature of seasonal breeding in birds, is important in production species, where egg production and fertility are affected by the photoperiod. Years of selection in meat-type birds have reduced the potential reproductive function, and the environmental manipulation of such genotypes is essential to maximise productivity. While it is known that egg-type pullets no longer exhibit photorefractoriness, and that female broiler breeders do, there is not much information about the response of male broiler breeders to photoperiod. Such information is important when designing lighting programmes for breeding stock, and this study aimed to gain more insight into the male response to photoperiod. A series of experiments was designed in order to achieve this. In the first the response of male broiler breeders to rearing on constant photoperiods was measured, and in the second the effects of age at photostimulation on age at sexual maturity were assessed. The response to an increase in photoperiod during the production cycle was investigated in the third trial. Evidence of photorefractoriness in males was observed, but this was not the case in all birds, possibly due to high variation in some of the fertility traits measured. It seems possible that males do not respond to photoperiod to the same extent as females. Unexpected observations of a response in some birds to early photostimulation, and the high variation observed prompted another experiment in which the heritability of the response to early photostimulation was measured as a potentially revolutionary method of selection, whilst checking that this response is not negatively linked to broiler growth rates. Left and right testis weight data, collected in the above experiments, were analysed for asymmetry. There was no consistent response in testes asymmetry to photoperiod, or evidence that asymmetry in testis weights is as a result of the imposition of genetic or environmental stress. The strong correlation found between testes dimensions and weight suggests that predictions of testis weights could be made through ultrasonics or laparoscopy.
A dynamic mechanistic anaylsis of the thermal interaction between a broiler chicken and its surrounding environment.
(2010) Blanco, Oscar Adrian.
Chickens, being open thermodynamic systems, maintain a constant exchange of energy and matter with their surrounding environment. In order to avoid reaching thermodynamic equilibrium with the environment the bird makes use of homeostatic mechanisms. These ensure the reduction of the entropy of the system to values that guarantee its integrality. The thermoregulatory response is a major component of the homeostatic machinery of living systems. This induces modifications of physiological parameters of the bird, taking the system “bird” to a new steady state. The achievement of this new state is possible only if the thermoregulatory mechanisms of the birds are able to counteract the environmental demand/burden. A successful thermoregulatory response depends not only on the achievement of that steady state, but also on the compatibility of the value of those parameters with life (especially regarding the value achieved by body temperature) as well as on the time of exposure to the environmental perturbation. Based on those premises, this thesis presents a mechanistic analysis of the thermal interaction between a broiler and its surroundings. The first section of the document introduces the reader to the general concepts of thermodynamics of living systems and physics of heat exchange. The second use mechanistic simulation techniques to represent the environment, the thermal and thermoregulatory properties of a broiler chicken and the interaction between bird and environment. Finally, the third section describes a conceptual simulation model able to predict, over a given period of time, the response of a bird to environmental conditions above those associated with least thermoregulatory effort. Various simulation exercises are reported, the objectives being to study the behaviour of certain variables and to question the validity of current theories of thermoregulation in environmental physiology.
Photic involvement in the reproductive physiology of female domestic fowl.
(2008) Lewis, Peter David.; Gous, Robert Mervyn.
No abstract available.
Modelling nutrient responses and performance of broiler breeders after sexual maturity.
(2007) Nonis, Magalie Kathy.; Gous, Robert Mervyn.
With the worldwide increase in consumption of poultry meat in recent years, the production of hatchable eggs from broiler breeding stock has become a critically important component of the poultry industry. Surprisingly, a perusal of the literature pertaining to broiler breeder nutrition leads to the conclusion that research nutritionists have neglected these birds. It has been assumed in many cases that the research on laying hens is applicable to broiler breeders. However, fundamental differences are apparent between the two strains that should be investigated more comprehensively if the potential of broiler breeder hens is to be achieved. Commercial laying hens have been selected predominantly for increased egg production whereas broilers have been selected for early rapid growth rate. By selecting for improved growth rate, both food consumption and mature weight of these birds has increased (Reddy, 1996), but because of the negative genetic correlation between body weight and egg production (Robinson et al, 1993) reproductive performance has not been improved. Broiler breeder hens differ from commercial laying hens, by their non-normal frequency distribution of egg outputs, their considerable lipid reserves, and by the fact that many do not lay in closed cycle. The practice of restricting feed intake during both the rearing and laying periods has become a standard management procedure in commercial broiler breeder operations and this differs from the manner in which commercial hens are fed. This raises important issues regarding the requirements of these birds for energy, amino acids and other essential nutrients, as the birds do not have the opportunity of meeting their nutrient requirements by adjusting food intake upwards when one or more of these nutrients is deficient in the feed. It is the duty of the nutritionist to provide the correct daily allowance of each nutrient in order to achieve maximum egg output by the flock, but given the variation between hens within a flock, such decisions need to be made on both biological and economic grounds. Improved strains are continually being produced by breeder companies, which exhibit better growth, feed efficiency and productivity. The way in which broiler breeder hens were fed in the past might not be the most effective way to feed the latest strains. Getting the right amount of feed with the right nutrient levels at the right time is the most important part of feeding broiler breeders, and to succeed their daily nutrient requirements need to be known. Information concerning the nutritional requirements of broiler breeder hens is limited in comparison to other types of domesticated poultry. However, enough information is available concerning energy and amino acid nutrition of this type of poultry to enable one to develop models useful for constructing accurate feeding programmes. The most appropriate way of estimating the nutrient requirement of broiler breeder hens during the laying period, or of optimising a feeding strategy, is by the use of simulation models. Emmans and Fisher (1986) suggested that a better approach to the problem of describing requirements and of expressing them quantitatively can be achieved by considering: firstly, the bird’s characteristics, secondly by defining resource scales carefully and thirdly by considering the quantities of each resource needed per unit of function. This approach has a greater chance of success than attempting to measure requirements by direct experimentation. Energy and amino acids are required for growth of tissues, egg production, maintaining normal body temperature, vital life functions and activity. For development of feeding programmes, we are most concerned with the three primary components, maintenance, growth and egg output. There are a number of factors that impact on the total nutrient requirement of the breeder. The maintenance component is affected by body size, environmental temperature, level of activity (housed in floor pens vs. cages) and possibly breed. Regarding the growth component, in the case of broiler breeders during lay the composition of growth needs to be addressed: whether this is only lipid gain or also includes protein gain. Lastly, the egg component is influenced by egg mass and hen age. In order to calculate energy and amino acid requirements, one must have knowledge of the requirements per unit of body protein weight, growth rate and egg mass. By continually monitoring the environmental conditions in the broiler breeder house, as well as body weight, egg weight and egg number, it is possible to estimate the state of the hens at any time and hence the optimum nutrient concentrations that should be fed the next day of the laying period by using the Breeder Model presented in this thesis. Optimising the feeding of broiler breeders during the laying period is made difficult because of the many interacting factors influencing their performance All the hens are not the same, they are not housed in the same environments, and the costs of feeding and the revenue derived from the sale of the product differs from one locality to another. The solution to this problem lies in the use of simulation models to describe the causal relationship between inputs and the predicted responses. This thesis explored new concepts and components for a simulation model to predict the nutrient requirement and performance of broiler breeders after sexual maturity.
The effect of nitrogen fertilization and stage of re-growth on the nutrititive value of kikuyu in the Midlands of KwaZulu-Natal.
(2011) Dugmore, Trevor John.; Nsahlai, Ignatius Verla.
Kikuyu pasture was fertilized at low and high levels of nitrogen (N), namely 50 and 200 kg N/ha, after mowing and clearing the plots, to induce low and high levels of N in the herbage. The subsequent growth was harvested at 20-, 30- and 40-d re-growth. These treatments were conducted in spring, summer and autumn. Treatments included level of N, stage of re-growth and season as variables in digestion trials using sheep and voluntary feed intake (VFI) trials using long yearling heifers in pens equipped with Calan gates. Nitrogen fertilization level had no impact on herbage dry matter digestibility (DMD). Stage of re-growth influenced digestibility in the spring and summer, the highest values recorded in the 30-d treatment. However, in the autumn, the 20-d re-growth recorded the greatest digestibility. Digestibility declined as the season progressed. Digestibility was not correlated to any of the chemical fractions measured in the herbage, including in vitro DM digestibility (IVDMD). Voluntary feed intake (VFI) followed a similar trend to digestibility, with peak values recorded for the 30-d treatment in the spring and summer, while the 20-d material induced the greatest intake in the autumn. Nitrogen fertilization had a negative impact on VFI over all seasons. Similarly to digestibility, VFI was not correlated to any of the chemical fractions measured, but was correlated to digestibility and moisture concentration of the herbage. Nitrogen degradability was determined using the in situ bag technique. Differences (p<0.05) were recorded for the quickly degradable N (a) and potentially degradable N (b) fractions within season, but not for the degradation rate of the slowly degraded fraction (c) per hour. The effective degradability (dg) was not influenced by N fertilization level in the spring, while N fertilization increased the dg values in the summer and autumn. Stage of re-growth exerted a positive effect (P<0.05) on the dg values. Rumen pH, rumen ammonia and blood urea nitrogen (BUN) levels were measured in rumen fistulated sheep. Rumen pH increased also with increasing level of N fertilization and declined with advancing stage of herbage re-growth in the autumn. Rumen ammonia increased with time of sampling post feeding to 4 hrs and then tended to decline by 6 hrs. Nitrogen fertilization level influenced rumen ammonia levels (p<0.05), with the low N level producing the lowest rumen ammonia levels. Rumen ammonia levels were highest at 20-d re-growth stage in summer and at the 40-d re-growth stage in autumn. DM concentration of the herbage had an inverse relationship with rumen ammonia. BUN levels were increased by high N fertilization and were positively correlated to rumen ammonia levels. Five years of digestibility data (82 digestion trials) and three years of intake trials (38 trials) data was pooled. These data, chemical composition of the herbage and the daily maximum temperatures, rainfall and evaporation recorded at and prior to the digestion and intake trials at Cedara were analysed using multiple regression techniques. Rainfall and temperature in the period of cutting and fertilization had a negative effect on digestibility, irrespective of the stage of re-growth at harvesting, 20, 30 or 40 days later, and a combination of the two proved significant, accounting for the most variance in DDM. Temperature depressed DMD by 11.4 g/kg DM per degree rise in temperature (Degrees C). Temperatures recorded during the cutting and fertilization phase were highly negatively correlated to VFI, irrespective of stage of re-growth. The DM concentration of the herbage as fed accounting for 32% of the variance in DMD, the NPN content of the herbage accounting for only 12.2% of the variance and the ash concentration of the herbage accounting for 15.9% of the variance in digestibility. Non-protein nitrogen was negatively correlated to VFI. Both DMD and VFI were highly negatively influenced by the moisture concentration of the herbage. Overall, the results of these trials demonstrated that environmental factors such as rainfall and temperature had a far greater impact on the digestibility of kikuyu herbage than the chemical composition, which had a minimal effect. Nitrogen fertilization did not influence herbage digestibility overall, but exerted a highly negative impact on voluntary intake.
Improving the nutritional representation of horse feeds in South Africa.
(2011) Young, Marion Belinda.; Laing, Mark Delmege.
Protein has been identified as a major reason that people purchase a horse feed, with anecdotal explanations offered for the poor prediction of response of horses to their rations, particularly in the sport horse market. The current research identifies through hierarchical cluster analysis that the myriad of riding feeds offered on the South African market fall into only four simple categories on the basis of wet chemistry. Feeds were subjected to the in vitro gas production technique (IVGPT) described by Pell and Schofield (1993), using equine faecal inoculum. Gas profiles, corrected for control fermentation profiles in the absence of substrate, were fitted to the model described by Campos et al. (2004) to derive GP kinetics. Gas production kinetics, and information in respect of pH, degradation efficiency, lag time and apparent and true digestibilities were obtained. The feeds were tested for glycaemic response in miniature horses using the hexokinase method with deproteinization using an auto analyser (Roche Diagnostics). Blood glucose parameters of feeds (mean, peak, slope and time to peak and area under the curve) in each group were compared by analysis of variance and regression with covariates. In vivo analysis of rates of passage and digestibility using using post-prandial percentages of acid insoluble marker collection was used to study the gastrointestinal process, to indicate foregut and hindgut compartmental flow. The need to balance nitrogen levels with a proportional supply of fermentable carbohydrate contradicts widely used protein intakes in the horse. In vitro fermentation was used in an analysis of nutrient synchrony, to identify optimal fermentative capacity for utilization of horse feeds. The characteristics of horse feeds were related to requirement and were composited in an analysis of the representation of horse feeds that would best reflect optimal utilization in the horse, to produce a method of feed characterisation that would lead to the optimal prediction of response of horses to feeds offered to South African horses.
The fibrolytic potential of domestic and wild herbivores microbial ecosystems on maize stover.
(2012) Fon, Fabian Nde.; Nsahlai, Ignatius Verla.
The growing demand for meat worldwide by the increasing human population (6.8 billion) calls for an increase in livestock production as well as attention to environmental sustainability. Production increases are critical especially in Africa with the highest annual population growth rate (2.5%), where most communities rely on livestock for protein supply. Attempts by intensive livestock farming to optimize production are limited by fibrous quality feeds (roughages) and their unavailability in both developed and developing countries. The overall objective of this study was to scan both domestic and wild herbivores in search for microbial ecosystems with superior fibrolytic potential that can be used as feed additives. It was hypothesized that microbes from wild herbivore can improve fibrous feed breakdown in domesticated ruminants. Experiment 1 evaluated the use of fresh or in vitro cultured faecal inoculum (FF) from two Jersey cows as a potential substitute for rumen fluid (RF). Cultured FF was a better substitute for fresh RF as demonstrated by percentage differences in exocellulase activity (0.4%) and true degradability (TD) (7%), compared to the differences observed between fresh RF and FF for exocellulase activity (33%) and TD (14%). It was applied in subsequent experimentation because it was cost effective (no surgery and reduced sample collection time). The second experiment compared the fibrolytic competence of cultured faecal inocula from three hindgut fermenters (miniature horse (mH), horse (H) and Zebra (ZB)) in summer and winter grazing in their natural environment. Both cellulase enzyme assays (exocellulase, endocellulase and hemicellulase) and in vitro maize stover digestibility study ranked the herbivores according to their fibrolytic competence as ZB > H > mH. The effect of cultured faecal inocula from H, ZB and wildebeest (WB) and its combined systems (N1=H+WB, N2=H+ZB, N3=WB+ZB and N4=H+WB+ZB) on the fermentation of maize stover were also evaluated in vitro. Both enzyme assays and MS degradability studies showed that the combined systems were higher (P<0.01) in fibrolytic activities compared to the individual systems. The microbial ecosystems were ranked as N1 > N2 > N4 > H > ZB > WB >N3; and N3 > N1 > N4 > WB > N2 > ZB >H by their exocellulase activity and degradability parameters, repetitively. The diversity of microbial ecosystems was confirmed by numerous active carboxymethyl cellulase bands present on a carboxymethy cellulose zymograms in experiment 4. The combined microbial ecosystems contain more active and variable bands of cellulases than in the individual microbial ecosystems. Systems N3 and N1 were considered as the best inocula for rumen transinoculation studies. Experiment 5 assessed the in vivo effect of direct-fed microbials from N1 and N3 on MS degradation, ruminal fermentation characteristics and cellulase enzyme profile in sheep. Feed dry matter intake increased (P<0.03) in N1 but tended to increase when inoculated with N3. The treatments, N1 and N3 increased (P<0.05) rumen exocellulase (9.4 and 33.2%, respectively) and endocellulase (82.1 and 47.1%, respectively) specific activities but not hemicellulase activity. Maize stover degradability parameters for N3 (TD, degradability of the insoluble fraction of MS, effective degradability, total SCFA and propionate) measured after 96 h of incubation tended (P>0.05) to be numerically different (1.1, 5.4, 7.1 and 7.9%, respectively). Increase in propionate for N3 was accompanied by higher total SCFA and lower CH4. A decrease in CH4 and no difference in CO2 allow both systems to be environmentally friendly since they have been associated with global warming. These studies showed that direct-fed microbials from N1 and N3 inocula have the potential of improving the utilization of maize stover feeds in ruminants, particularly in view of its simplicity and availability which allows it to be implemented at a relatively lower cost compared to other specific strains or microbial cultures. However, more research is required to identify, purify and classify the superior fibrolytic microbes in the most active ecosystems.
Feeding behaviour, diet selection of goats and nutritive value of browse species in sub-humid subtropical savannah, South Africa.
(2012) Basha, Nasreldin Abdelrahim Dafaalla.; Scogings, Peter Frank.; Nsahlai, Ignatius Verla.
Diet selection and its variation due to difference in forages nutritive value are central processes in plant-herbivore interactions. An incorporating of these parameters may allow predicting diet selection patterns which are a basic underpin for sustainable vegetation management and profitable animal production. To achieve these issues many studies were done two of which were run to study the browse-browser interactions in a sub-humid subtropical savannah, a herd of goats was used as a model browser in natural pasture. Other studies evaluated the nutritive value of five plant species which were the most selected by goats. The objectives of this study were to (i) determine the seasonal patterns of diet selection of goats on woody species and their nutritive value and (ii) to predict the diet selection. The secondary objectivrs were to (i) investigate how plant characteristics such as plant morphology (spinescence, and broad vs. fine leaves), phenology (evergreen vs. deciduous species) and plant chemistry (nitrogen, neutral detergent fibre, acid detergent fibre, acid detergent lignin, condensed tannin, cellulose and hemicellulose) are relate to the diet selection patterns and to (ii) evaluate the nutritive value of the most plant species selected by goats during the different seasons. Two experiments were conducted at Owen Sitole College of Agriculture, KwaZulu-Natal, to determine diet selection of goats grazing/browsing in Zululand Thornveld. The first experiment was done in the early wet season (November 2007) and late wet season (March/April 2008) while the second experiment was conducted in the dry season (June/July 2008), early wet season (November/December 2008) and late wet season (February/March 2009). The relative abundance of browse species in the veld was determined and used to estimate the selection index. In the first part, diet selection was estimated using (i) direct observation of animals (account bouts) by observing every one minute two goats while they were foraging with others for 3 hours in the morning and 1.5 hours in the afternoon on alternate days for a total of six days and (ii) an indirect plant-based method by observing at regular intervals 40 marked branches on ten plants of each browse species every two days for a total of six days. The browse species observed were: Gymnosporia senegalensis, Acacia nilotica, Acacia karroo (Acacia natalitia), Scutia myrtina and Dichrostachys cinerea. In both seasons, the three most selected species according to the plant-based observations were S. myrtina, A. karroo and D. cinerea. Consistently, A. nilotica experienced moderate defoliation and G. senegalensis the least. However, on the basis of the selection index, the species followed the order: A. nilotica > D. cinerea > A. karroo > S. myrtina > G. senegalensis in the early wet season and A. nilotica > S. myrtina > D. cinerea > A. karroo > G. senegalensis in the late wet season. Both methods did not rank species in the same order. The selection index was negatively (P<0.05) correlated to neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). In the second part, observations were taken on feeding time of two goats, randomly selected per day for 7-8 days. Observations were made during active foraging periods for 2 hrs in the morning and 1.5 hrs in the afternoon. The duration of each feeding bout and the species of woody plant from which bites were cropped at each feeding station were recorded. Season and plant species affected diet selection and preference. The five main species selected (utilized) by goats in decreasing order were S. myrtina, A. nilotica, D. cinerea, Acacia natalitia and Chromolaena odorata. Scutia myrtina was the most preferred (highest utilisation relative to availability) in the dry season while D. cinerea comprised the greatest proportion in the early and late wet seasons. Scutia myrtina was most preferred in the dry and early wet seasons while A. nilotica was most preferred in the late wet season. Spinescent species were generally selected more than non-spinescent species in all seasons, while fine-leaf and deciduous species were selected more than broad-leaf and evergreen ones in the wet seasons. However, preference for broad-leaf and evergreen species increased in the early wet season. Although plant chemistry varied across seasons, it did not explain the preference of goats for various plant species in this study. Instead, effects of chemistry were species- specific. The nutritive value of the five main species selected by goats was evaluated by chemical composition, in vitro gas production, in vitro degradability and in sacco degradability. Two experiments were conducted for the in vitro studies, the first experiment was to test the effect of season and species, while the second experiment tested the biological effect of tannins using polyethylene glycol 4000 (PEG). The PEG treatment was applied to samples of the early and late wet seasons only. The parameters were maximum gas production (GP), degradation rate (C), lag time (lt), maximum rate of GP at the point of inflection (μ), half time to the maximum gas volume(T1/2), gas produced from fermentation of soluble and slowly degradable fractions (A and B, respectively), their degradation rates (c1 and c2, respectively), apparent (ApDeg) and true degradability (TrDeg), microbial yield (MY), partitioning factor (PF), degradation efficiency factor (DEF) and short chain fatty acids (SCFA). There were wide variations among seasons and species in crude protein (CP), NDF, ADF and condensed tannins. Season and species affected kinetics of gas production, GP, TrDeg, MY, PF and SCFA. Chromolaena odorata had the highest CP (185.8-226.4 g kgˉ¹), GP (87.3-104.1 ml gˉ¹ DM), gas produce from soluble (47.6-50.9 ml gˉ¹ DM) and insoluble (39.8-50.9 ml gˉ¹ DM) fractions during the three seasons compared to other browse species. The TrDeg ranged from 634 to 856 g kgˉ¹ DM. The total SCFA varied between seasons and among species. The addition of PEG decreased TrDeg and PF, and increased GP and total SCFA. The GP, its degradation rate (C) and gas from the soluble fraction were positively correlated to CP without and with PEG. Gas from the soluble fraction was negatively correlated to NDF, ADL and CT; and GP to CT without PEG. In the in sacco study, the parameters of dry matter (DM) and nitrogen (N) degradability were soluble (a) and slowly (b) degradable degradability, the degradation rate (c), potential degradable (PD), effective degradability (ED) and lag time (lt). Season affected PD of DM degradability and ED of both DM and CP. Browse species and its interaction with season affected all parameters except b fraction of CP and interaction did not affected PD of CP. Chromolaena odorata had the highest estimated parameters of degradation during the three seasons compared to other browse species. Based on PD and ED, the plant species followed this decreasing order: C. odorata, A. nilotica, A. natalitia, S. myrtina and D. cinerea. All parameters were positively correlated to CP except the a and b fractions of DM and CP, respectively, and lt of both DM and CP. All parameters were negatively correlated to NDF, ADF and ADL except the b fraction and rate of degradation. Condensed tannins (CT) were negatively correlated with all parameters except the b fraction and PD of DM and CP, and lt of DM degradation. Cellulose was negatively correlated with a of DM and lt of CP degradation. The broad objective of this study was to assess whether plant characteristics, in sacco degradability, in vitro gas production, digestibility or chemical composition (NDF, ADF, ADL, CT and CP) could predict the selection of browse species. The parameters were selection index, plant characteristics (spinescence, or leaves phenology), chemical composition, in vitro gas production, in vitro degradability and in sacco degradability parameters. Most of these parameters were poor for predicting selection by goats of browse species. Spinescence (spn), leaves phenology (phen), NDF, CP and CT accounted for 86% of the variation in selection index (y) = -5.91 - 0.01CT - 0.002NDF + 0.02CP + 6.18spn + 2.43phen; (R2=0.86; n=20; RMSE=0.406; P<0.001; for phen, 1 = evergreen, 0 = deciduous; for spn, 1 = spinescent, 0 = spineless). It was concluded that in vitro gas production, in vitro degradability and in sacco degradability were poor predictors of selection index of browse species used by goats. Spinescence, leaf phenology, condensed tannins, CP and NDF were predictors of diet selection index and suggested that these plant species have potential to be used as feed supplements. Chromolaena odorata has the highest potential as feed protein source in goats. The addition of PEG (tannin binding agent) emphasizes that the inhibitory effect of tannins on rumen microbes was great in tannin-rich feeds.
Integrated control of gastrointestinal nematodes of sheep using plant extracts. and bicontrol agents.
(2013) Ahmed, Mawahib Alhag Ali.; Laing, Mark Delmege.; Nsahlai, Ignatius Verla.
Infection of small ruminants by gastrointestinal nematodes (GIN) is a major health concern because they cause substantial economic losses, especially in the tropics and sub-tropics. For many years, control of GIN has been based upon use of anthelmintics. However, there is now a global challange because mutant GIN individuals can tolerate most of the widely used anthelmintics. Therefore, alternative control measures are needed. The objective of the study was to screen a number of plant species for their anthelmintic effects, and to evaluate selected strains of Bacillus thuringiensis (Berliner) and Clonostachys rosea (Schroers) for activity against sheep GIN. Subsequently, the combined treatments would test a dual control strategy for nematodes by using a combination of plant extracts with biocontrol agents. Ethanol extracts of 25 plant species were screened for their anthelmintic effects against Haemonchus contortus (Rudolphi 1803). Extracts of each plant were used in vitro at various concentrations (10, 20 and 30%) to treat 10 day faecal cultures. Five plants with high efficacies (Ananas comosus L. Merr., Aloe ferox Mill., Allium sativum Linn., Lespedeza cuneata Dum. Cours. and Warburgia salutaris Bertol.f. Chiov) were selected for further investigation, using ethanol, dichloromethane and water extracts at four concentrations (2.5, 5, 10 and 20%). Ethanol was the most effective solvent. Larval counts decreased as a result of increasing extract concentrations. An ethanolic extract of Lespedeza cuneata caused more than 70% mortality at all concentrations. In an in vivo study, the five plants A. comosus, A. ferox, A. sativum, L. cuneata and W. salutaris extracts were compared to a positive Control (Equimax®, a modern anthelmintic based on abamectin and praziquantel). Gender, eggs count (EPG₀) and initial body weights were used in assigning sheep (24 females and 24 males) to six groups. Each group was randomly assigned a treatment. Plant extracts were applied as an oral dose (100 mg kg⁻¹ BW), one dose per week per animal for 42 days (Phase 1). Subsequently, the same sheep were dosed for three consecutive days with the same treatments, keeping them in the same groups (Phase 2). Rectal faecal samples were taken for counting of eggs per gram of faeces (EPG) and L₃ larvae per gram (LPG) in faecal cultures. With application of plant extracts, the EPG count decreased with time (P<0.001), and the impact of the plant extracts increased (P<0.001) with time. Two extracts, from A. comosus and L. cuneata, were the most effective in Phase 1 (58% and 61% reduction of EPG, respectively,), and in Phase 2 (77% and 81% reduction of EPG, respectively). In a study on potential biocontrol agents, two strains of Bacillus thuringiensis (Bt) and one of Clonostachys rosea f. rosea (C. rosea), and compared with a diatomaceous earth (DE) product for their anthelmintic activity in sheep. Bacillus thuringiensis and C. rosea were fed to sheep at a rate of 1g kg⁻¹ BW, and DE was fed at 2% of sheep diet. The biocontrol treatments had no effect on EPG (P>0.05), but reduced GIN larvae per gram (LPG) (P<0.001) in faecal culture. Efficacy varied with time (P<0.001). By Day 7 Bt, C. rosea and DE had caused mortalities of GIN of 75.7, 86.9 and 60.6%, respectively. In addition, the efficacy of feeding 1g kg⁻¹ BW of C. rosea chlamydospores to sheep every day, every second day and every third day was tested. Daily feeding of fungal chlamydospores reduced LPG (a count of 12±1.67 GIN larvae) (P<0.001) more than feeding them the biocontrol agent every second day (39±0.77) or third day (58±1.77). By Day 12, feeding the biocontrol agent to sheep every day, every second day, or every third day caused mortality of GIN larvae of 90, 63 and 49%, respectively. Four dietary levels (treatments) of C. rosea (0.25g (F1), 0.5g (F2), 1g (F3) and control (C) of C. rosea product kg-1 BW) were tested. Treatments were each mixed with a complete diet and fed to sheep once daily for 10 weeks, according to body weights. Increased doses of the biocontrol agent reduced LPG (P<0.001), larval development (LD) (P<0.001), and increased efficacy (P<0.001). On Day 70, F1, F2, F3 and the Control controlled LD by 33.3, 72.3, 89.4 and 2.6%, respectively. Clonostachys rosea was effective in reducing third stage larvae (L₃) on pastures significantly (P<0.001) by Day 63 and Day 70. Ethanolic extracts of A. comosus, A. ferox, A. sativum, L. cuneata and W. salutaris all reduced egg production by GIN parasites of sheep. Feeding sheep cultured chlamydospores of a biocontrol fungus, Clonostachys rosea, reduced counts of nematode larvae in sheep; and 1g C. rosea chlamydospores kg⁻¹ BW daily was enough to reduce nematode infective larvae, therefore reducing the degree of pasture contamination. An initial trial showed that the combination of the two treatments of an A. comosus extract and C. rosea chlamydospores was more effective than either treatment on its own in controlling gastrointestinal nematodes in sheep. A long-term trial is being undertaken currently to confirm this finding.
Effects of hydric stress on the growth, blood chemistry and meat quality characteristics of indigenous chickens.
(2013) Chikumba, Nation.; Chimonyo, Michael.; Nsahlai, Ignatius Verla.
The broad objective of the study was to determine the effects of restricted water intake on the growth, blood chemistry and meat quality characteristics of indigenous chickens in semi arid environments. A total of 15 flocks in communal villages and 12 flocks in resettlement schemes of Msinga District in South Africa were monitored for 30 months to determine the effects of production system and season on flock size, dynamics and constraints faced by indigenous chicken producers. As a follow up, 281 and 233 chicks hatched in November 2011 from 18 and 9 households in communal villages and resettlement schemes, respectively were monitored using a structured checklist to determine survival and causes of mortality from hatching up to 12 weeks of age. Kaplan-Meier survival distributions and the odds ratios for effects of potential risk factors were determined using survival analysis and logistic regression models, respectively. Flock composition and structure were significantly affected by production system and month. Farmers in resettlement schemes had approximately one cock and three hens more (P < 0.05) than those in communal villages. The number of growers and chicks were similar (P > 0.05) between the two production systems but chicks were the predominant age group (38 %) of each flock. The cock to hen ratio in households in communal villages was 1:3.5, while that in resettlement schemes was 1:3.7, suggesting that inbreeding might have been reducing flock productivity. Flock sizes in communal villages peaked in March (45.1 ± 3.02) during the post rainy season and declined steadily to a low of 34.7 ± 3.63 in September during the hot-dry season. The largest flock sizes in resettlement schemes were observed in January (52.4 ± 5.09) during the hot-wet season and the smallest in August (36.1 ± 5.98) during the cold- dry season. Households in communal villages had more chicks (P < 0.05) than cocks, hens and growers throughout the year except in June when the number of growers was equal to that of chicks. In resettlement schemes, the number of chicks was lower (P < 0.05) than the number of hens and growers, except in June and July when it was equal to that of growers. Total entries were not affected (P > 0.05) by production system. Hatched chicks were the major mode of entry, accounting for more than 97 % of entries into flocks. The contribution of purchases, gifts and exchanges was negligible. Mortality was the main cause of exits from flocks, accounting for 70 and 63 % of total exits among households in communal villages and resettlement schemes, respectively. The major causes of mortality were aerial predators, sub-optimalnutrition and inclement weather conditions, which were similar between production systems. The number of birds that exited flocks through slaughter for household consumption was higher (P < 0.05) among households in resettlement (34% of total exits) than communal villages (21 % of total exits). The proportion of chickens exiting flocks through sales was higher in communal (9 %) than resettlement (4.3 %) households. Chick survival from hatching to 12 weeks was higher (P < 0.05) in communal villages (55 ± 3.14 %) than in resettlement schemes (41 ± 4.19 %). Mean chick survival time did not differ (P > 0.05) between communal (56 ± 3.30 days) and resettlement (49 ± 3.23 days) flocks. Provision of water ad libitum and treatment of sick birds were important covariates in prolonging the survival time of chicks. The effects of restricted water intake on growth performance, blood chemistry, physicochemical properties, and sensory characteristics of meat from Naked Neck (NNK) and Ovambo (OVB) chickens were also assessed. In the experiment, 54 pullets of each strain with an average weight of 641± 10g per bird were randomly assigned to three water restriction levels for 60 days in a completely randomized design. The treatments were ad libitum, 70% of ad libitum and 40% of ad libitum water intake. Each treatment group was replicated three times. The pectoralis (breast) muscle was sampled for meat quality, fatty acid composition and sensory quality analyses. Ovambo chickens had superior body-weight at 16 weeks of age, average daily gains (ADG) and average daily water intake (ADWI) than NNK chickens. Body weight of birds at 16 weeks of age, ADG, average daily feed intake (ADFI), ADWI and water to feed ratio (WFR) declined progressively (P < 0.05) with increasing severity of water restriction, while food conversion ratio (FCR) values increased (P < 0.05) as the severity of water restriction increased. Naked Neck chickens had better FCR at the 40 % of ad libitum water intake level than OVB chickens. The dressing percentage per bird was higher (P<0.05) in water-restricted birds than those on ad libitum water consumption, irrespective of strain. Heart weight was significantly lower in birds on 40% of ad libitum water intake than those on ad libitum and 70% of ad libitum water intake, respectively. Packed cell volume was higher (P < 0.05) in NNK than OVB chickens offered waterad libitum, but similar in birds offered 70 and 40 % of ad libitum. There were no differences in erythrocyte count (RBC) and mean corpuscular volume (MCV) values between strains, but MCV was higher in birds on 40 than 70 % of ad libitum water intake, irrespective of strain. Naked neck chickens had higher (P < 0.05) white blood cell count (WBC) values than OVB chickens at 40 % restriction level, but lower WBC than OVB at 70 % water restriction level. Uric acid, creatinine, triacylglycerides, total cholesterol, low density lipid cholesterol, total protein and globulin increased (P < 0.05) with each increment in water restriction, but the increase in creatinine and total cholesterol was more pronounced in OVB than NNK chickens. The opposite was observed for uric acid. Alanine transaminase, alkaline phosphatase and aspartate transaminase activities were not influenced by strain and water restriction. It was concluded that the two strains could withstand up to 40 % of ad libitum water restriction, but NNK chickens tolerated water stress better than OVB chickens. Water intake levels of 40% of ad libitum produced meat with significantly lower (P < 0.05) cooking loss, and higher (P < 0.05) redness (a*) values in NNK chickens compared with OVB chickens. Water intake level had no effect (P > 0.05) on lightness (L*) and yellowness (b*) values, shear force, moisture and protein contents in both strains. The fat content of NNK meat was 41 % lower (P < 0.05) than that of OVB meat at 70 % of ad libitum, but 31 % higher at 40 % of ad libitum water intake. The ash content was significantly elevated (P < 0.05) in birds on 70 % of ad libitum compared to those on ad libitum and 40 % of ad libitum water intake, which had similar (P > 0.05) ash contents. Birds on 40 % of ad libitum water intake had significantly higher (P < 0.05) proportions of octadecanoic acid (C18:0), cis, cis-9,12-octadecadienoic acid (C18:2 ῳ-6), cis-8,11,14,17-eicosatetraenoic acid (C20:4 ῳ-6), cis-7,10,13,16-docosatetraenoic acid (C22:4 ῳ-6), cis-4,7,10,13,16,19-docosahexaenoic acid (C22:6 ῳ-3), total polyunsaturated fatty acid (PUFA), total omega-3 PUFA and total omega-6 PUFA proportions, but lower (P < 0.05) cis-7-hexadecenoic (C16:1c7), cis-9-octadecenoic (C18:1c9), cis-11-octadecenoic acid (C18:1c11), cis-13-docosenoic acid (C22:1c13), total monounsaturated fatty acids than those on the 70% of ad libitum and ad libitum water intake, respectively. The proportion of trans-9-octadenoic acid (C18:1t9) was higher (P < 0.05) in NNK chickens on 40 % of ad libitum water intake than OVB chickens. It was concluded that water restriction at 40 % of ad libitum water intake resulted in favourable cooking loss values and meat redness (a*) values, omega-3 and 6 PUFA proportions and a high ῳ-6/ῳ-3 ratio. The high fat content of NNK chickens at 40 % of ad libitum water intake compared to OVB chickens suggests a superior adaptation to hydric stress. Naked Neck breast meat had higher initial impression of juiciness scores than that from OVB chickens, but only in birds on ad libitum and 70 % of ad libitum water intake. Sensory scores for first bite, connective tissue and tenderness decreased with increasing severity of water restriction (P < 0.05). Aroma, flavour and atypical flavour were not affected by strain or water restriction level (P > 0.05). There were significant strain differences for sustained impression of juiciness and tenderness, with the highest scores occurring in NNK chickens (P < 0.05). Aroma had a significant influence on the flavour of breast meat (P < 0.05). Fat content was significantly correlated with initial impression of juiciness, first bite and sustained impression of juiciness of breast meat. It was concluded that water restriction up to 40 % of ad libitum had a significant and adverse impact on juiciness and first bite scores of meat.
Mechanisms of resistance to Rhipicephalus ticks in Nguni cattle reared in the semiarid areas of South Africa.
(2013) Marufu, Munyaradzi Christopher.; Chimonyo, Michael.; Dzama, Kennedy.
Ticks and tick borne-diseases (TBD) are major challenges to cattle production among smallholder farmers in the semiarid areas of South Africa. Nguni cattle have been reported to be resistant to ticks and TBD, however, the mechanisms responsible for the trait are not fully understood. The broad objective of this study was to determine the mechanisms of resistance to ticks in Nguni cattle reared in the semiarid areas of South Africa. Tick infestation levels, body condition scores (BCS), packed cell volumes (PCV) and the molecular prevalence of A. marginale were determined in Nguni (n = 70) and local crossbred (n = 79) cattle reared in the semiarid areas of South Africa. Relationships among skin thickness, hair length, coat score and tick counts were assessed in seven to nine month old Nguni (n = 12) and Bonsmara (n = 12) heifers. As a follow up, cutaneous hypersensitivity responses to unfed larval extracts (ULE) of the ticks Rhipicephalus decoloratus and Rhipicephalus microplus were examined in heifers to determine host immunity to the ticks. Tick counts and inflammatory cell infiltrates in skin biopsies from feeding sites of adult R. microplus ticks in nine-month-old Nguni and Bonsmara heifers were also evaluated. The molecular prevalence of A. marginale was similar in the Nguni (47.7 %) and local crossbred (52.3 %) cattle. Nguni cattle suffered less severe losses from and were more vi resilient to A. marginale infection than local crossbreds. Nguni heifers had lower coat scores, hair length and tick counts than the Bonsmara heifers. The relationship between tick counts and coat score was positive and linear in the Nguni (y = 1.90x – 0.40) and quadratic in Bonsmara (y = -7.98x2 + 12.74x - 3.12) heifers. Bonsmara cattle showed a more intense immediate reaction and no delayed hypersensitivity reaction to ULE of Rhipicephalus ticks. Nguni heifers presented a less intense immediate reaction and a delayed hypersensitivity reaction at 72 h post inoculation with ULE of Rhipicephalus ticks. Reactions to R. decoloratus ULE produced a more intense skin response at all time intervals in both breeds than that of R. microplus. Parasitized sites in Nguni heifers had higher (P < 0.05) counts of basophils, mast and mononuclear cells than those in the Bonsmara heifers. Conversely, parasitized sites in Bonsmara heifers had higher (P < 0.05) neutrophil and eosinophil counts than those in the Nguni heifers. Tick count was negatively correlated (P < 0.05) with basophil and mast cell counts. There was a positive correlation between eosinophil counts and tick counts in both breeds, and between tick counts and mononuclear cell counts in the Bonsmara breed. It was concluded that smooth and short coats, delayed type hypersensitivity and cutaneous basophil and mast cell infiltrations are responsible for increased tick resistance in the indigenous Nguni cattle breed of South Africa.
Effects of physicochemical properties of fibrous feed on feeding behaviour and gut health of growing and finishing pigs.
(2013) Bakare, Archibold Garikayi.; Chimonyo, Michael.
The broad objective of the study was to determine feeding behaviour and gut health of pigs fed different fibres at varying inclusion levels. Maize cob, maize stover, sunflower hulls, veld grass, sawdust, lucerne and dried citrus pulp were used in growing and finishing pig diets to provide a wide range of physicochemical properties. Time spent eating, drinking, lying down, sitting/standing and other activities was observed using video cameras. Blood samples were collected at the end of the trial for both growing and finishing pigs for analysis of glycated haemoglobin, albumin, globulin, total protein, creatine kinase, urea and uric acid. Intestinal segments were collected at the end of trial for growing pigs to determine mucosal architecture of the intestines. Digestible energy (DE), bulk density (BD), acid detergent fibre (ADF) and water holding capacity (WHC) were the most important variables predicting time spent on different behavioural activities in growing pigs (P < 0.001). Water holding capacity, neutral detergent fibre (NDF) and ADF were the most important variables involved in predicting time spent on different behavioural activities in finishing pigs (P < 0.001). Physicochemical properties influenced time spent on different behavioural activities and they provided relationships with time spent on different behavioural activities in both growing and finishing pigs. Glycated haemoglobin, albumin, globulin, total protein and uric acid were factors that influenced time spent eating in growing pigs (P < 0.05). In finishing pigs, only serum total protein was selected as the best predictor variable influencing time spent eating (P < 0.05). The blood metabolites were correlated with time spent eating and drinking. They provided threshold values with time spent eating and drinking by pig. Hence, they can also be used as potential biomarkers that modulate neuronal pathways which reduce time spent eating and drinking. In this study, bulk density (BD) and NDF were the best predictor variables influencing villi height (VH) and apparent villi surface area (AVSA) in pigs (P < 0.05). Grouped pigs fed fibrous diet spent more time eating, lying down, standing, walking and fighting (P < 0.05). Skin lesions appeared the most on neck and shoulder region followed by chest, stomach and hind leg region, and finally head region (P < 0.05). Fibrous diet did not reduce aggressive behaviours, rather aggressive behaviours emanated out of frustration when queuing at the feeder. It was concluded that physicochemical properties of fibrous diets and nutritionally-related blood metabolites influence feeding behaviour. Mucosal architecture was also influenced by physicochemical properties of the fibrous diets.
The productive response of broiler breeder hens to lighting and growth manipulation during rearing.
(2003) Ciacciariello, Mariana.; Gous, Robert Mervyn.
This study was designed to provide information that would enable the development of a theory to predict age at sexual maturation and settable egg production in broiler breeder hens submitted to a variety of constant or increasing photoperiods and with diverse growth curves. Six trials were conducted using three strains of broiler breeder females housed in floor pens or individual cages. The treatments covered a wide range of growth profiles during the rearing period, from slow growth to achieve 2100g at 24 weeks, to fast growth achieving 2100g at 15 weeks of age. The lighting treatments included 8, 11 and 16-h constant photoperiods, photostimulation at various ages between 10 and 24 weeks, abrupt or gradual increases in daylength, and transfers to a 10, 11, 12 or 16-h final photoperiod in lay. The results show that broiler breeders exhibit photorefractoriness, and that the adult form starts developing from about 56 weeks of age. They also suggest that photorefractoriness contributes towards the accelerated decline in egg production observed at the end of the laying period. Relaxations of feed restriction during the rearing period and earlier transfers to a stimulatory photoperiod were successfully used to advance sexual maturity by up to 3 weeks compared with conventionally managed controls. Furthermore, birds subjected to constant photoperiods reached sexual maturity later than birds that had been photostimulated at 20 weeks of age. Settable egg production progressively improved when birds were transferred to stimulatory daylengths at older ages, until about 20 weeks, but subsequent delays in photostimulation did not result in any further increase in egg numbers. Delaying photostimulation of conventionally grown birds beyond 28 weeks and maintaining them on constant 8 or 16-h photoperiods negatively affected egg production. Maintaining birds on constant 11-h photoperiods had a less deleterious effect on egg production. Increasing the photoperiod from 8 to 12 h resulted in a significant improvement in settable egg production compared with birds transferred to 16 h. Prediction equations were produced to estimate mean age at sexual maturity for control birds subjected to constant photoperiods, and for birds reared on a control or fast growth curve and photostimulated at between 10 and 24 weeks of age. Data presented in this thesis suggest that, to minimise the accentuated decline in egg production typically seen late in the laying period, birds kept in light-tight houses should be transferred to photoperiods shorter than the currently recommended 16 h. Finally, photorefractoriness provides an improved understanding of the causes of erratic performance frequently observed in out-of-season flocks kept in open sided houses.
A stochastic model to predict annual egg production of a flock of laying hens.
(2004) Johnston, Shelley Anne.; Gous, Robert Mervyn.
Ovulation rate in laying hens is determined by the interaction of two biological systems; namely, a circadian rhythm that restricts the release of luteinising hormone to an eight- to ten-hour period of the day, and the process of follicle maturation. Etches and Schoch (l984) used a two-compartmental model to represent the circadian rhythm and a Gompertz equation for follicle maturation. In doing so, they were able to predict ovulation times for two- to nine-egg sequences. This model has been improved by replacing their table of values with continuous functions that predict the values for each parameter in the ovulatory model, for any ovulation rate. Consequently, ovulation times may be predicted for any sequence length. A population model that simulates annual egg production has been developed in Visual Basic. Each parameter in the model is allocated a mean and standard deviation, so that variation is introduced into the flock. Mean age at first egg is predicted from the age at photostimulation and the lengths of the photoperiods applied during rearing. Quadratic-by-linear functions are used to predict changes in the hen's internal cycle length over time, which in turn determine changes in the ovulation rate and rate of lay. Short egg sequences, frequently observed at onset of lay in experimental flocks, are simulated initially, followed by the prime (or longest) sequences, which are produced at the time of peak rate of lay, before gradual increases in the internal cycle length cause the egg sequences to become shorter once more. In view of the fact that the interval between oviposition and the subsequent ovulation is about 30 minutes, time of lay may be predicted from ovulation time for all eggs other than the last egg of a sequence, because in this case there is no associated ovulation. A curvilinear function is used to predict the value of the last interval from the ovulation rate, because experimental data show that short sequences have longer intervals between the last two eggs than long sequences. The circadian rhythm of LH release is linked to the onset of darkness, so that mean time of lay occurs 13 to 14 hours after sunset. The distribution of oviposition times is unimodal for young flocks and bimodal for older flocks. Yolk weight is predicted from hen age using a function appropriate for the genotype. Allometric functions are used to predict albumen weight from yolk weight and shell weight from the weight of the egg contents. Egg.weight is given by the sum of the three components. With advancing hen age, the proportion of yolk in the egg increases at the expense of both albumen and shell. Random events, such as internal ovulations, and the production of soft-shelled and double-yolked eggs, are accounted for in the model. Their incidence is linked to the genotype and to the age of the hens and their occurrence is restricted to a proportion of the flock. Internal ovulations cause interruptions to egg sequences, thereby reducing overall mean sequence length. This model could be of benefit to a producer wanting to know how a change to the lighting programme would affect the laying performance of the strain, or to a nutritionist desiring to determine changes in voluntary feed intake and to the nutrient requirements of the birds over the laying period. It may also be used as a teaching aid, so that students gain a thorough understanding of the process of egg production and are able to test the response of layers to different environmental stimuli. The user has control over a number of inputs, thereby making it a generalised model that can be used for different strains. With a few modifications, the model may be used to simulate the erratic and variable laying behaviour of broiler breeders.
The potential of pods from tree legumes as supplement to low quality roughages for ruminants.
(2002) Thomas, Ngwa Asanji.; Nsahlai, Ignatius Verla.
The goal of the study was to examine the use of pods from tree legumes as supplements to poor quality roughage-based diets. Trials were carried out to address issues related to the nutrient content of the pods and their limitations as supplements due to the presence of anti-nutritional factors. In the first trial (Chapter 3), the chemical, mineral and amino acid compositions of pods from six tree species were examined. The rumen degradation of the dry matter, nitrogen and cell wall constituents of the pods were evaluated, using the nylon bag technique. In trial 2 (Chapter 4), different rumen ecologies were created in fistulated sheep by feeding pasture hay in combination with different pod meals and alfalfa (50:50), in order to examine the effects of anti-nutritional factors (present in the pods) on the degradation of dry matter and fibre constituents by ruminal microorganisms. Trial 3 (Chapter 5) further examined the effects of anti-nutritional factors on the production of volatile fatty acids (VFAs) and on the activities of microbial enzymes in the rumen. In trial 4 (Chapter 6), ensilage was examined as a means of detoxification of cyanogenic glycosides in the pods of Acacia sieberiana and molasses as well urea were evaluated as preservatives that could improve the aerobic stability of the silage produced from the pods of A. sieberiana. In trial 5 (Chapter 7), the silage and four other feeds (3 pod meals and alfalfa) were used in a choice feeding trial to study the effect of anti-nutritional factors on the palatability and intake of the feeds by goats and sheep, using hay as the standard feed for comparison. Trial 6 (Chapter 8), evaluated the use of the silage with or without wheat bran as supplements to a roughage basal diet fed to lambs. Intake, digestibility of dry matter, organic matter, cell wall constituents, nitrogen retention and weight gain were considered as indices for examining the potential of the supplements. Chapter 9 presents a general discussion on the attributes and limitations of pods as supplements. It also leads to a conclusion on the importance of browse in tropics and raises the need for further research on this class of feeds. The results of the work show that pods from tree legumes are rich in nitrogen and minerals and may provide sufficient ammonia (71-85 mg/l of rumen fluid) in the rumen that could enhance the growth and/or activity of rumen microorganisms. The maintenance of rumen pH by the pod meals at a range of 6.2-6.4 gives an additional advantage over other supplements that contain high concentrations of soluble carbohydrates because cellulolytic activity by rumen microbes is said to be optimal around this pH range. The importance of pods as supplements was however, reduced by the presence of anti-nutritional factors (especially condensed tannins) which had a very high concentration (28%QE) in the pods of Acacia sieberiana. The results of the feeding trial showed a positive correlation with the intake of the basal diet and weight gain when pods meals were included in the diet at moderate levels (30% of total dry matter intake). This is an indication that the pod diets were able to maintain a conducive rumen environment for microbial activity and at the same time, provided by-pass protein through the formation of protein-tannin complexes which leave the rumen at near neutral pH but in the abomasum (pH 3-4), the protein was liberated and digested by gastric enzymes to provide amino acids that were utilized by the host animal. However, when the pod meal was increased to 50% of total intake (Chapters 4 and 5), the concentration of condensed tannins in the diet depressed the degradation of cell wall constituents, production of VFAs and reduction in the activity of fibrolytic enzymes in the rumen. Ensilage was found to be effective in reducing the concentration of cyanogenic glycosides by 80% when the pods of A. sieberiana were ensiled for a period of 35 days. The resulting silage was relished by both goats and sheep in a choice feeding trial, an indication that besides the benefit of reducing this important anti-nutritional factor, ensilage enhanced the intake and palatability of these pods. Molasses and urea improved the fermentation process, the nutritive quality and the aerobic stability of the silage. The important conclusions drawn from the results of this work are that, at low concentration, tannins are beneficial to ruminants by protecting plant proteins from excessive degradation in the rumen thus preventing bloat and increasing the quantity of dietary protein reaching the lower gastro-intestinal (GI) tract. However, at higher concentrations, the effect of condensed tannins is rather detrimental, both to the ruminal microorganisms and the host animal, mainly through their binding effect with proteins and structural carbohydrates and precipitation of both microbial and gastric enzymes, with the net effect of reducing the digestibility of the roughage-based diet. Further research is necessary to better quantify the concentration of anti-nutritional factors in this class of feeds in order to optimize their utilization by rumen microorganisms and host animal, taking into account the fact that the concentration varies according to the plant species, stage of maturity of the plant and the environment in which the plant is found. It should also be born in mind that the biological effects of different tannins depend on the characteristics of the specific tannin (condensed or hydrolysable), the animal species and possibly the nutritional status of the animal, particularly whether the animal is tannin-naive or tannin-adapted.
The influence of energy density on the performance of feedlot cattle.
(2002) Dominy, Neil John.; Nsahlai, Ignatius Verla.; Lishman, Arthur William.
This study examined the interaction of diets differing in their energy densities and heat increments of feeding on the feed intake patterns, physiological measurements, empty body composition, and animal performance of steers in a feedlot environment. The energy densities of the diets ranged from 7.97 to 11.83 MJ ME and 6.50 to 9.53 MJ Effective Energy (BE) and the ratio of EE to ME ranged from 0.79 to 0.84. The feed intake pattern of steers was not affected by differences in the diets energy densities but was affected by diets that differed in their heat increments of feeding. The physiological measurements, rectal temperatures measured at 9.00 am and 2.00 pm (TR 9.00 am and 2.00 pm) and respiration rates of steers in the feedlot were compared to control steers kept on pasture. Steers in the feedlot registered significantly (P < 0.001) higher physiological measurements than the controls and the accepted norms for cattle not under heat stress. A relationship exists between the pattern of physiological measurements over time and feed intake pattens over time. Physiological measurements peak and dip during the same weeks as the feed intakes peak and fall. Peaks and the immediate dips thereafter are related to points of acute response resulting in a chronic response and acclimatisation. All feedlotted steers experienced heat stress within the first week of feeding. Steers feedlotted in summer took 28 days to achieve their peak feed intake whereas steers feedlotted in winter required 42 days to reach their peak feed intake. Steers that required 42 days in which to reach their peak intakes had greater increases in their daily intakes than those that required 28 days to reach their peak intakes. Steers feedlotted in winter lost their winter coat between weeks three and six. Differences in peak feed intakes were recorded for animals of a heavier starting live weight (late versus early maturing and long yearling versus weaners). Peak feed intake increased in line with increasing live weight at the start of feedlotting. These differences were attributed to their greater surface area and hence greater heat loss capacity. Comparison of steers tissue deposition rates of steers on diets differing in their ratio of EE to ME revealed non significant differences in the growth rates of protein and lipid. The proportional use of energy intake was significantly different with significantly (P < 0.1) more of the daily energy intake being utilised for lipid deposition in diets with a higher heat load. Animals suffering from differing heat loads were inhibited in depositing protein but were able to deposit lipid due to the associated lower heat production. This enforced deposition of lipid results in animals reaching slaughter condition after similar lengths of time but at lower ADG and lower carcass weights. The economic consequences are that the returns are higher due to higher carcass gains for steers fed diets with a higher ratio of EE to ME.
The effects of excess dietary crude protein on the efficiency of utilization of protein by broiler chickens.
(2002) Swatson, Harry Kofi.; Gous, Robert Mervyn.
No abstract available.
Productivity of South African indigenous Nguni goats possessing Synergistes jonesii bacteria on Leucaena Leucocephala-grass and natural pastures.
(2002) Akingbade, Adebayo Abel.; Nsahlai, Ignatius Verla.; Morris, Craig Duncan.
The main objectives of the study reported in this thesis were to investigate the cause of poor conception and high pre-weaning kid mortality rates among South African indigenous Nguni goats (SAING) maintained on Leucaena leucocephala-grass pasture (LGP), and the potential of natural pasture (NP) and improved pasture (LGP) for the productivity of the mimosine-susceptible SAING breed after receiving dihydroxypyridone (DHP)-degrading rumen bacteria (Synergistes jonesii) via animal-to-animal transfer. Seasonal variation in forage quality and mimosine contents of two Leucaena leucocephala varieties, detection of S. jonesii from rumen digesta, effects of feeding Leucaena foliage on semen quality, grazing activities and blood metabolite profiles during gestation and reproductive performance prior and post kidding were evaluated. Aspects relating to reproductive performance prior and post kidding, colostrum and milk constituents, growth performance and blood profiles of weaned and unweaned kids, dams-to-kid transfer of S. jonesii, protein and energy requirements of the SAING kids were also examined. Cultivar Cunningham was better suited for the location ofthe study than cv. Spectra because it was available during ten months of the year compared to the six months of cv. Spectra availability. Growth performance, reproductive performance and overall productivity of SAING maintained on LGP were better than those of their counterparts on NP. Benefits of LGP during gestation include higher body weight gain of does, higher incidence of twin multiple births and higher birth weight of kids compared to values on NP. Higher milk yield, earlier return to first postpartum oestrus and better pre-weaning growth of kids relative to values obtained on NP, were the benefits of maintaining SAING on LGP during lactation. Over the entire study, conception on LGP treatment compared favourably to that on NP. Feeding Leucaena foliage did not have any detrimental effect on semen quality and fertility of the SAING bucks. Feeding LGP as gestation or/and lactation feed had no detrimental carry-over effect on the post kidding reproductive performance of SAING does and kids. The kids were also able to acquire S. jonesii from dams via animal-to-animal transfer.

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