Doctoral Degrees (Animal and Poultry Science)

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A description of the chemical and physical growth of New Zealand white and chinchilla rabbits.
(2024) Eniwaiye, Adenike Adetutu.; Rani-Kamwendo, Zikhona Theodora.
This study investigates two key aspects in animal science: (i) describing the growth potential and chemical composition of two commercially bred rabbit strains, in order to optimize the composition of their feed based on variables predicted by simulation modelling; (ii) testing the hypothesis that the allometric relationship between body parts remains consistent across different strains, sexes, and body protein levels. In other words, the research assesses whether animal scientists have faced challenges in modifying the proportional relationship between the weight of different body parts of rabbits and their body protein weight. The primary goal of the study was to outline the physical and chemical transformations in the body composition of two commercially bred rabbit breeds, namely New Zealand White and Chinchilla, over a 126-day growth period. The key focus was on investigating how the growth performance of developing rabbits is affected by sex and age, considering the influence of body protein. Moreover, the research examined alterations in growth and variations in the physical and chemical elements of the body. To achieve the objectives, series of studies were conducted: In this experiment, a total of 220 rabbits, consisting of both New Zealand White and Chinchilla strains, were utilized. Weekly weighing of 100 rabbits from each strain were conducted, starting from day 14 (due to the fragility of the kittens at birth) and continuing until day 140, in order to assess the growth potential of each rabbit. Additionally, samples were collected from 120 rabbits from each strain at specific ages: day 14, 21, 28, 35, 42, 56, 70, 84, 112, and 140. Before slaughter, the animals underwent weighing to determine their weight exclusive of internal organs. Post-slaughter, their weight was measured again to discern the weightof internal organs, skin, and the weight without the skin. The dissected body parts were weighed, labeled, and stored in a freezer for subsequent thawing and mincing. The specimens were then subjected to freeze-drying to extract water content. Following this, they underwent further grinding before being analyzed for protein, lipid, and ash. Moreover, the Gompertz equation was applied to individual body parts and the protein weight of each body component. The parameters of the Gompertz equations were defined as the final weight of these components, their rate of maturation, and the time required to achieve the peak growth rate of each component. By utilizing data from each individual rabbit, allometric regressions were employed to establish the relationship between the weights of physical and chemical components. The natural logarithm of body protein weight served as the independent variable, while the natural logarithm of body component weight served as the dependent variable. A significant allometric relationship was found between body weight and pelt weight, as the weight growth process occurs continuously from birth to maturity. Body weights and chemical composition of males and females (bucks and does) of the two strains remained similar throughout the trial. Mature body weights for both strains (New Zealand White and Chinchilla) at 140 days averaged 1760 g and 1558 g; mature body protein weights averaged 95 g/kg and 61 g/kg; and mature body lipid contents averaged 40 g/kg and 55 g/kg, respectively. Rates of maturing per day of body weights for males and females of both strains averaged 0.0241 and 0.251; pelt-free, 0.0294 and 0.0251, and body lipid was 0.0441 and 0.0225, respectively. The rates for body protein differed between New Zealand White females and Chinchilla females (0.0172 vs 0.0256/d). Separate equations were needed for males and females to describe the allometric relationships between lipid and protein in the pelt-free body. The rate of maturing of pelt in the New Zealand White was higher in females than in males (0.0249 vs 0.0214/d), and the mature weight was lower in females than in males (45vs 52 g/kg), respectively. Common values of the sexes for both strains are represented when there were no apparent variations in the constant terms and regression coefficients. The saddle weights, regardless of the protein content in both sexes of the New Zealand White, can be described by a single constant term of 1.0193, and a lower single constant term value of -1.1070 in the Chinchilla rabbit. The goodness of fit (R2) for both strains was highest in the saddle with 0.974 and 0.957 in the New Zealand White and Chinchilla gigantas rabbits, respectively, while it was lowest (0.922) in the pelt of New Zealand White and hindlimb (0.892) of the Chinchilla gigantas rabbits. Sexes differed in the allometric relationships of all component parts measured in both breeds. A common relationship between the two strains could be used to predict the weights of all rabbit major component parts. Further studies are recommended to confirm the findings of this study. Keywords: Chemical, Chinchilla, Components, Physical, New Zealand white, Rabbits.
Antioxidant activity of Vachellia species, pork quality and fatty acid composition from pigs supplemented with graded levels of Vachellia tortilis leaf meal.
(2017) Khanyile, Mbongeni.; Mapiye, C.; Chimonyo, Michael.
Abstract available in PDF file.
Aspects of the copper-molybdenum-sulphur interactions in sheep.
(1979) Van Ryssen, Jannes Bernardus Jansen.; Stielau, Werner Johannes.
No abstract available.
Behaviour, physiological responses, meat yield and gut morphology of free-range chickens raised in a hot environment.
(2016) Mutibvu, Tonderai.; Chimonyo, Michael.; Halimani, Edward Tinyiko.
It is vital to minimise thermal stress and associated welfare problems for birds reared in hot environments and behaviour is a good indicator of thermal stress. The broad objective of the study was to investigate behavioural, physiological and gut morphological responses of free-range slow-growing chickens raised in a generally hot environement. A total of 488 Naked Neck (NN), Ovambo (OV) and Potchefstroom Koekoek (PK) chickens were used in the study. The experiments conducted in this study explored effect of strain, sex, rearing system and provitamin A bio-fortification of maize on gut development in chickens in the context of thermal stress. Two hundred and eighty-eight NN, OV and PK chickens were separated by sex and reared in either intensive or extensive rearing pens, with twelve birds from each strain per pen. Time budgets on free-ranging and related behavioural activities were determined at 3 different observation periods (0800 h, 1200 h and 1600 h) for 3 weeks. Body weight (BW), random environmental effects; ambient temperature (Ta) and relative humidity (RH) as well as bird stress indicators; rectal temperature (RT), heart rate (HR), breathing rate (BR), tonic immobility (TI), spleen and liver weights were determined for the free-ranging and confined flocks. On the last day of the trial, blood samples were collected from randomly selected birds via brachial venepuncture. Body weight (BW), carcass weight (CW), dressed weight (DW), portion and giblet yields were determined. Gut organs were recovered and weighed on a digital scale within 10 min of slaughter. Intestinal length, weight, ileal villus parameters; villus height (VH), villus density (VD), villus width (VW) and muscularis externa (ME) thickness and apparent villus surface area (aVSA) were assessed. Ambient temperature (Ta) and RH were used to compute a temperature humidity index (THI) and data were subjected to ANOVA with strain, sex and rearing system as the main effects. Time of day influenced (P < 0.01) free-ranging-related behaviours namely; foraging, drinking and preening. Females spent more time compared to males on the same activity and also appeared, generally, more stressed than males. Physiological responses of PK, OV and NN were generally comparable under similar rearing conditions and none of the factors studied had an effect (P > 0.05) on RT. Sex influenced (P < 0.05) VH, aVSA, VW and gizzard weight. Villi were taller, wider, hence greater aVSA in males than females on WM and PABM while ME thickness decreased (P < 0.01) between 18 and 21 weeks of age. Strain influenced (P < 0.05) VW, aVSA, ME thickness, intestine length, liver, gizzard, pancreas and heart weights. Sex of bird influenced (P < 0.05) carcass weight (CW), heart, proventriculus and abdominal fat pad (AFP) weight. The heart, liver and pancreas weights were significantly higher in OV than PK and NN chickens. Strain influenced (P < 0.05) BW, H/L ratio, spleen, relative liver weights, thigh, neck, pancreas, gizzard and crop weights but not TI (P > 0.05). Sex of bird affected (P < 0.05) BW, spleen, relative liver weights, H/L ratio, shank, drumstick and abdominal fat pad (AFP) and pancreas weight. Strain × sex interactions were observed (P < 0.05) on spleen and liver weights. There was negative correlation between time spent foraging and THI. Higher BW and heavier portions were obtained with OV than with NN and PK chickens. Generally, males yielded heavier portions than females of the same strain. Free-range birds experienced crop and gizzard hypertrophy and pancreas atrophy. Free-range males yield heavier cuts and females were fattier than males. It was concluded that rearing system, strain and sex of bird influence gut morphology, physiological responses, meat and fat yield in free-range slow-growing chickens. While free-ranging could minimise stress in birds, mechanisms should be devised to prevent predation in outdoor rearing of birds. Endo- and ecto-parasite infestation, behavioural studies using more elaborate techniques and evaluation of fatty acid profiles are possible areas of future research to help understand, hence improve bird welfare for slow-growing chickens in outdoor systems.
Biological and economic response of laying hens to dietary isoleucine, methionine, lysine and energy.
(1980) Griessel, Munro.; Gous, Robert Mervyn.
No abstract available.
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.
A description of the genotype of pigs using simulation modelling.
(1996) Ferguson, Neil Stuart.; Gous, Robert Mervyn.
No abstract available.
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.
Ecological benefits of brachiaria grasses in integrated crop-livestock production systems in Rwanda.
(2016) Mupenzi, Mutimura.; Nsahlai, Ignatius Verla.
A study was conducted with the broad objective to evaluate ecological benefits of Brachiaria grasses in integrated crop-stall-fed livestock production systems in humid and semi-arid region of Rwanda. The specific objectives of the study were: (1) To identify factors that determine household feed resource supply and willingness to plant improved fodder in humid and semi-arid regions of Rwanda; (2) To determine nutritive values of available feed resources used by smallholder farmers in Rwanda; (3) To determine biomass and nutrient productivity as well as cutting management of promising Brachiaria genotypes for semi-arid ecologies in Rwanda (4) To determine nutritional value of Brachiaria species, on stall-fed replacement dairy heifers with or without concentrate supplements; (5) To examine the biophysical and physiological basis that make Brachiaria grass a more palatable and nutritious forage with impact on lactation in dairy cows relative to Napier grass. A structured questionnaire was administered to 204 households of semi-arid and humid environments and used to determine major livelihood options and characterise integrated crop-livestock production systems. Farming was the major livelihood strategy among households in semi-arid and humid areas. The diversity of livestock species including, dairy cattle among households were more in semi-arid than in humid environments. Milk yield was higher in Jersey than in other dairy cows under smallholder farm prevailing conditions. Logistic regression analysis showed that age, level of education and experience in livestock rearing of household head significantly influenced adoption of planted forages in smallholder farms in both areas. Farmers in semi-arid area were twice more likely to establish improved fodder species in farmland than those from humid areas. Napier grass and a variety of crop residues were the major feed resources in both the rainy and dry seasons in both areas. Feed resource inventorying depicted a wide (n=24) species diversity from both on-farm and off-farm source five of which were unique to semi-arid areas. Chemical composition, ii contents of metabolisable energy (ME), organic matter digestibility (OMD) and neutral detergent fibre digestibility (NDFd) and rumen fermentation characteristics partitioning factor (PF) were highly variable, depicting variability in their efficiencies of utilisation in microbial functions and post-ruminal nutrient supply for maintenance and production. Brachiaria genotype and cutting management study involved an evaluation of five cultivars (cv.) of Brachiaria brizantha, one cultivar of B. humidicola, two cultivars of Brachiaria hybrid and one cultivar of Brachiaria decumbens against Napier grass (Pennisetum purpureum) in an on-farm trial in a completely randomised block design (RCBD) with four replicates. Forage samples were collected at 60, 90 and 120 days after planting (DAP). Samples of each cultivar and age of cutting were analysed for concentration of dry matter (DM), crude protein (CP), organic matter (OM), neutral detergent fibre (NDF), minerals, in vitro apparent degradable dry matter (ivADDM), metabolisable energy (ME) and in vitro gas production (GP) kinetics. The DM, CP, OM, ivADDM and digestible OM increased from 60 to 90 DAP and declined thereafter. The NDF contents increased while CP contents decreased consistently with increase in age. Macro and micro-nutrient concentrations were also higher at 90 DAP. The ME differed (P<0.05) among grasses and between DAP. The GP of grasses cut at 90 DAP was higher than the other two DAP. The highest yield cultivars were Basilisk, Marandú and Piatá. The optimum age of cutting was species specific, but overall cutting at 90 DAP was recommended. In a study on changes in growth performance of crossbred dairy heifers under cut-and-carry feeding system, sixteen crossbred (Ankole × Jersey) heifers (Average body weight 203±35 kg) were randomly allocated to two dietary treatments. Brachiaria hybrid cultivar Mulato II with 2 kg/day of commercial concentrates (MCC) and Napier grass (Pennisetum purpureum) with the same supplement (NCC) were fed to heifers for 12 weeks. Feeds, mineral lick and water were provided ad libitum. Absolute daily dry matter intake (g DM/day) and relative intake (g/kg of metabolic body weight - BW0.75) were higher in heifers fed on MCC than in heifers fed on NCC (P<0.001). Feed conversion ratio was lower (P<0.001) in MCC than NCC diets. Final body weight (FBW) and body weight gain (BWG) did not differ between the two groups of heifers (P>0.05). Average daily weight gain (ADWG), also not differed significantly (P>0.05). To determine biophysical factors affecting quality of Brachiaria sp. and impact on performance in crossbred dairy cattle, a feeding trial was conducted using 40 lactating crossbred (Ankole × Holstein Friesian) in second parity and in 10–15 days in milk in collaboration with 40 farm households. Experimental diets were Brachiaria brizantha (cv. Piatá) and Napier grass (Pennisetum purpureum–used as control) as sole or mixed forage with Desmodium distortum (70:30 w/w fresh basis). Chemical analysis showed that Napier was low in DM, OM, and CP, but higher in NDF and ADF than the test Brachiaria (P<0.001). The composition varied with duration of the experiments (P<0.05) but not across farms (P>0.05). Voluntary intake did not differ across diets (P>0.05) but was consistently higher in Piatá-based than in the Napier-based diets. Average milk production with higher in cows fed on the test Brachiaria-based than in the Napier-based diets (P<0.001). Cows fed grass-legume mixes recorded higher milk than sole grass diets. Digesta flows and degradation rates were also rapid in grass-forage than in sole grass diets (P<0.001). The most promising cultivars identified from this study were cv. Basilisk, cv. Marandú and cv. Piatá, because of its nutritional characteristics as well as nutrient yields which were higher and more comparable with Napier grass than other grass cultivars. The feeding trial with replacement dairy heifer proved that depriving these animals the nutritional advantage associated with selectivity in forages did not compromise the nutritional value cv. Mulato II; hence, this cultivar can effectively be used as quality fodder for cut-andcarry dairy system. Digestive physiology of Piatá-based diet provided a strong, but indicative evidence of the differences in palatability, voluntary intake and impact on lactation between cv. Piatá and Napier grass. These differences might have associated with physical effectiveness of NDF.
The effect of diluent on the bacterial reaction to disinfectants.
(1973) Hathorn, Fergus Ask Shuldham.; Abbott, C. W.
No abstract available.
The effect of form of nitrogen on the efficiency of protein synthesis by rumen bacteria in continuous culture.
(1991) Kernick, Brian Louis.; Van Ryssen, Jannes Bernardus Jansen.; Mackie, Roderick Ian.
The aim of this study was to examine the effect of the form of nitrogen available to mixed rumen bacteria on the efficiency of microbial protein synthesis. A novel, solid substrate, continuous culture fermentor which proved capable of maintaining representative populations of mixed rumen bacteria under steady state conditions, at predetermined growth rates was developed for the study. A series of experiments wherein maize straw, alkaline hydrogen peroxide-treated wheat straw, rye grass or a mixture of maize straw and maize starch were used as substrates were performed in the fermentor. The effect of supplementing these substrates with different forms of nitrogen, namely peptides in the form of a partial hydrolysate of casein, or ammonium salts alone or ammonium salts plus branched-chain volatile fatty acids, on digestion of the substrate and microbial protein synthesis was investigated. Supplementation of maize straw with peptides increased microbial protein synthesis, however this was only significant (P<0.05) when the availability of nitrogen and specific growth rate of the bacteria were not limiting. Organic Matter digestion was not affected by peptide supplementation. Replacement of casein hydrolysate with sunflower oilcake as a source of amino acid nitrogen further increased microbial protein synthesis. The form of nitrogen supplementation did not affect the digestion of constituent cell wall monosaccharides of maize straw. Supplementation of alkaline hydrogen peroxide-treated wheat straw with either branched-chain volatile fatty acids or casein hydrolysate increased the synthesis of microbial protein significantly (P<0.05) and caused a slight, but insignificant increase in the digestion of cellulose-glucose. The efficiency of microbial protein synthesis on rye grass was high, relative to the other substrates, and unaffected by the supplementation of either branched-chain volatile fatty acids or peptides. On media containing high levels of starch, microbial protein synthesis as well as Organic Matter digestion were increased by peptide supplementation, but these differences were only significant (P<0.05) when the bacteria were growing at a high specific growth rate. In all of these experiments, peptide supplementation was accompanied by extensive degradation and deamination of amino acids which offset any increase in microbial protein synthesis. Peptide supplementation therefore resulted in far less efficient overall utilization of protein.
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.
Effect of roughage processing and feeding level on production, reproduction, and growth performance of the Red Maradi goat.
(2016) Abdou, Nourou.; Nsahlai, Ignatius Verla.; Gouro, Abdoulaye S.
Abstract available in PDF file.
The effect of stocking rate on the performance of beef cows and their progeny in the highland sourveld areas of Natal.
(1988) Van Niekerk, Alvin.; Lishman, Arthur William.
In three separate. but related studies, the performance of weaner/replacement heifers, dry pregnant cows, and first calvers and mature cows and their progeny, at different stocking rates in the Highland Sourveld, was investigated. The study area was located in Bioclimatic region 4e in the Province of Natal, Republic of South Africa. In the first study, carried out over four seasons, the effect of winter and summer nutritional levels on the performance of replacement heifers, bred at two years of age, was investigated. The results of this study indicated that compensatory growth was a potentially important factor in reducing feed costs, but the degree of compensation was highly dependent upon stocking rate and the condition of the veld. The most economical regime for rearing heifers up to the mating stage was a low growth rate (0 - 0,25 kg/day) during the first winter (post weaning) followed by a low stocking rate (0,75 AU/ha) on summer veld. Treatment did not generally affect the number of heifers attaining puberty, nor their conception rates. Pregnancy rates as high as 96% were achieved. Treatment also had no apparent effect on subsequent calving rates. In the second series of experiments, the role of condition scoring as a management tool in the Highland Sourveld was studied. The condition score of the cow was shown to be an important factor determining conception rate and time of conception. Only 8% of the cows mated at a condition score of 1,5, conceived, whereas 80% conception rates were achieved when the cows were mated at a condition score of 3,0 - 3,5. The cost of improving a cow's condition from 1,5 to 3,0 was R108, whereas the cost of improving a cow's condition from 2,0 to 3,0 was R54. In the third study, carried out over nine consecutive seasons, the effect of stocking rate and lick supplementation on the performance of iactating cows and first calvers was investigated. Four stocking rates were applied - 0,83, 1,0, 1,25 and 1,67 cows plus calves per hectare. The very high stocking rate was terminated after four seasons because of a significant decline in both cow and calf performance, and the severe deterioration of the natural pasture. There was no benefit to either the cows or calves with access to a urea-based lick at the very high stocking rate, but at the low stocking rate (1,0 cow + calf/ha) the cows were in such a condition that the grazing season could have been extended, thereby saving on winter feed costs. First calvers produced weaners as heavy as those of the mature cows and were in similar body condition at the end of the grazing season. The excellent performance of the first calvers was attributed largely to the fact that they calved 3 - 4 weeks prior to the mature cows. The grazing behaviour of the first calvers and the mature cows, at the different stocking rates, was observed in the fourth study which was carried out over two consecutive seasons. There were no significant differences in the grazing time between the first calvers and the mature cows at any of the stocking rates. In all the treatments, the first calvers appeared to establish the grazing patterns, with the mature cows adopting a followership role. Alloparental behaviour was noted in the early part of both grazing seasons.
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.
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.
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.
Estimation of carcass composition of beef cattle by the urea dilution technique.
(1977) Kock, Schalk Willem.; Stielau, Werner Johannes.
No abstract available.
Exploring the use of indigenous knowledge to mitigate tick challenges in goats.
(2020) Mkwanazi, Mbusiseni Vusumuzi.; Chimonyo, Michael.
Farmers in developing countries with limited access to orthodox veterinary care commonly use indigenous knowledge. Indigenous knowledge (IK) stems out of peoples' ingenuity, credulity and long insatiable curiosity of the environment and nature that is often passed from one generation to the next. The broad objective of the study was to investigate the use of indigenous knowledge and practices to control ticks in goats. A qualitative study was conducted to explore indigenous practices and methods used to control tick infestation in goats from Jozini Municipality of uMkhanyakude District in South Africa. Data collected included common ticks and associated tick challenges in goats, effects of ticks in goats, new tick species and diseases that have developed. Indigenous methods and practices used to control ticks and associated tick challenges were also captured. Source of knowledge, transference of knowledge to other community members or household members were also requested. Indigenous people have substantial knowledge on ticks exemplified by their ability to differentiate between different tick species. Ticks are traditionally identified using colour patterns and feeding sites. Ticks cause wounds, skin irritation and limping. Nine medicinal plant species were identified to control ticks and their associated challenges and four used to treat tick -borne diseases. A cross-sectional survey was conducted to determine the extent of use of the IK to control tick infestation in goats. Amblyomma tick species were ranked as the most important amongst the tick species, followed by Rhipicephalus evertsi evertsi ticks. A significant population of farmers (81%) depended on the use of tick sprays, whereas others used injections (3%). Cissus quadrangularis L. (Inhlashwana) was the most used ethno-veterinary plant to control ticks with a frequency of (64%), followed by Gomphocarpus physocarpus E. Mey (Uphehlacwathi) (56%). There was no association between the use of IK and cattle, sheep, chicken ownership (P >0.05), although, households that kept cattle less than 30 were using IK more than those with larger herd sizes. The most important purpose of using IK was that it is effective. Farmers older than 55 years were 2.89 times more likely to influence the extent of use of IK compared to farmers less than 30 years who were mostly young farmers. The likelihood of having the presence of herbalist in the particular rangeland was 3.64 times more likely to influence the use of IK (P < 0.05). To determine the relationship between tick count and coat characteristics, BCS, FAMACHA score a total of 96 Nguni goats of different ages based on dentition and sex were used. Weaners had lower tick counts compared to does and bucks. During the hot-dry season, BCS declined faster as tick count increased (p <0.01), compared to the post rainy season. The number of ticks increased (p <0.01) in the hot-wet season linearly as BCS increased whilst, during the cool-dry season, BCS decreased (p <0.01). The rate of change of BCS was higher in weaners as tick count increases compared to does and bucks. There was no relationship between BCS, FAMACHA and PCV on weaners (p >0.05). In the in vitro study aqueous plant extracts were applied at (6, 12 and 18% (v/v) and compared to a commercial acaricide, Eraditick (amitraz) positive control and negative control (distilled water). Extraction solvents used were methanol and acetone. The repellency percentage was highest at 6% v/v for acetone, methanol, and control (distilled water) extracts similar to positive control Amitraz. The acaricidal efficacy of the Gomphocarpus physocarpus at 12% v/v of methanol extracts was as good as that of 6% v/v, however different to that of 18% v/v was relatively low. The mortality rate of the positive control reached 100% after 72 hrs (p < 0.05) post-treatment, though it was similar to that of acetone, methanol, and control across different concentrations. The 6% v/v of Cissus quadrangularis for each extract were more effective (p<0.01) against Rhipicephalus evertsi evertsi ticks. Repellency percentage of Cissus quadrangularis and different extraction solvents declined with time from 30 min to 5 hrs. It was concluded to achieve sustainable veterinary care there is a need to integrate the two knowledge systems into coming up with viable tick control strategies to enhance goat productivity. Also, it is important that when IK policies are implemented, factors that promote its utilisation need to be considered including the participation and interaction of IK custodians. Findings from this study also indicated that tick count increases during hot-wet and hot dry season in goats and cause substantial decline in BCS. It is crucial, therefore, to put measures to counteract the drop in BCS, and increase in tick counts with season, if productivity of the goats is to be improved. Also, ticks can be reduced efficiently in goats using IK, more especially the use of Cissus quadrangularis.Lin and Gomphocarpus physocarpus at a concentration of 6% v/v.
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.

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