Doctoral Degrees (Animal and Poultry Science)

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The influence of variations in the level of nutrition on reproduction in the ewe.
(1972) Lishman, Arthur William.; Stielau, Werner Johannes.
No abstract available.
The effect of diluent on the bacterial reaction to disinfectants.
(1973) Hathorn, Fergus Ask Shuldham.; Abbott, C. W.
No abstract available.
Estimation of carcass composition of beef cattle by the urea dilution technique.
(1977) Kock, Schalk Willem.; Stielau, Werner Johannes.
No abstract available.
The importance of age at first calving, relationship between body mass and fertility and feeding systems on production in the beef female.
(1978) Meaker, Helgaard Johannes.; Lishman, Arthur William.
No abstract available.
Aspects of the copper-molybdenum-sulphur interactions in sheep.
(1979) Van Ryssen, Jannes Bernardus Jansen.; Stielau, Werner Johannes.
No abstract available.
Biological and economic response of laying hens to dietary isoleucine, methionine, lysine and energy.
(1980) Griessel, Munro.; Gous, Robert Mervyn.
No abstract available.
Response of broiler chickens to dietary lysine, methionine and metabolisable energy concentrations.
(1981) Maclachlan, Rais Guthrie.; Stielau, Werner Johannes.; Gous, Robert Mervyn.
No abstract available.
Luteal function during early post partum in the ewe.
(1984) Grobbelaar, Johan.; Lishman, Arthur William.
No abstract available.
Intensive beef production on cultivated pastures in a sub-tropical environment.
(1984) Louw, Brian Peringuey.; Lishman, Arthur William.
The comparative performance of spring-calving beef cowherds comprising either Dual Purpose (Simmentaler) or British-cross (Hereford x Africaner) cows and calves was investigated at stocking rates of 3,0, 4,12, 5,34 and 6,74 cows and calves/ha on Kikuyu pasture over three seasons. An increase in stocking rate was associated with a decrease in the length of the grazing period, an increase in the mass and condition loss of cows, a decrease in calf livemass gains, a decrease in milk production, an increase in the production of beef per hectare and a decrease in margins over feed costs per cow. Stocking rate did not influence reconception rates, which averaged 65% over the three seasons. Simmentaler cows produced calves approximately 2 kg heavier at birth and 24 kg heavier at weaning, approximately 1,4 litres of milk more per day, lost more condition and attained higher margins over feed costs per cow and per hectare than Hereford-cross cows. Season influenced the length of the grazing season, birth mass, livemass gains in calves and mass changes in cows. Milk production accounted for 40% of the variation in calf gains on pasture. The conversion of milk to calf gain was influenced by milk yield, stocking rate, breed and calf sex. Ovarian and endocrinological responses associated with normal and restricted suckling for a 15-day period at two postpartum stages (Days 35 to 50 and 60 to 75) were examined in Bos taurus and Bos indicus cows. All cows received progestagen therapy, followed by GnRh administration during the periods of variable suckling intensity. Restricted suckling exerted little influence in Bos taurus cows, but tended to improve the ovulatory response, to decrease the incidence of "short" cycles and to increase reconception rates in Bos indicus cows. Treatment exerted no influence on calf growth and on tonic LH and oestrogen secretion. Bos indicus cows suckled normally released more LH in response to GnRh than Bos taurus cows. Bos indicus cows suckled once daily secreted less LH in response to GnRh than those suckled normally. Seasonal effects on tonic LH, and progesterone secretion were studied in cycling Friesland cows. Mean tonic LH levels during autumn were significantly higher than those during summer and spring. Season. exerted no influence on progesterone secretion.
The influence of suckling during early lactation on the resumption of ovarian activity and oestrous behaviour in the Afrikaner cow.
(1986) Wells, Peter Lee.; Lishman, Arthur William.
No abstract available.
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.
Testing the libido of breeding sires to predict mating performance in the field and the hormonal control of male sexual behaviour.
(1988) Crichton, James Spencer.; Lishman, Arthur William.
The incidence of sexually low-response rams was determined in a group of 31 young Ile de France stud rams by means of three libido tests. Eight rams ( 25,8%) we reclassified as being sexually low-response. The proportion of rams showing normal sexual behaviour did not increase over the three tests. As testing progressed the incidence of mounting behaviour increased significantly. The increase in serving activity was non-significant. Following flock mating two low-response rams had not marked any ewes and showed preference for homosexual company. Five of the eight low response rams had a common sire and it is suggested that sexual behaviour may be influenced genetically. A group of 20 month-old beef bulls (n=54) representing nine breeds were evaluated for libido using five serving capacity (SC) tests (bulls tested in groups) followed by one libido score test (bulls tested as individuals). Bos indicus bulls displayed significantly lower SC than bulls from exotic breeds. Bulls underwent a definite learning process over the five SC tests. The increase in SC was not significant for all breeds. The use of oestrous teaser females held no advantage over the use of properly restrained non-oestrous females. Agonistic behaviour did not depress SC (individual exceptions were noted). Growth rate did not have a consistent effect on SC. Activity on the libido score test was highly significantly correlated to SC. The influence of night or day and the presence or absence of an observer on the SC of 20 month-old Bos indicus bulls (n=18) was evaluated over 12 SC tests. Bulls showed no preference for nocturnal sexual behaviour and were not hindered by personnel scoring SC. The improvement in SC with progression of the tests suggested some form of adaption to pen test conditions and/or learning experience. Serving behaviour was however inconsistent from test to test indicating that restrained females do not represent the ideal stimulus. Agonistic interaction depressed SC. Subsequent pasture mating behaviour was significantly related to SC. Some of the factors influencing pasture behaviour are discussed. High SC bulls achieved a conception rate that was 10,8% higher than that of the low SC bulls (difference non-significant). The relationship between bull libido (libido score test) and conception rate following a 21 day breeding season was investigated over two seasons. The average bulling percentages were 2,9 and 2,5% in the first and second seasons respectively. High libido bulls had no advantage over medium libido bulls in both seasons. Bulls achieved acceptable conception rates (> 70%) in both years and it is suggested that the commonly recommended bulling percentage of 4% is conservative. In an investigation into the hormonal control of sexual behaviour in the ram the technique of active immunization against specific steroid hormones was used in an attempt to highlight the possible central action of dihydrotestosterone (DHT) on mounting behaviour. The central aromatization of testosterone gives rise to DHT and oestradiol (E2). Immunization against E2 and a combination of oestrone (E1) and E2 in testosterone propionate (TP) implanted wethers reduced mounting behaviour to animals (no exogenous hormone). levels seen in control Results suggest that DHT has no or limited central nervous action. The effect of DHT appears to be largely via its sensitization of the penis which enhances mounting behaviour in DHT+E2 implanted wethers to levels higher than those recorded in E2 implanted wethers but similar to the activity recorded for wethers receiving TP implants.
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.
Theoretical and applied aspects of voluntary feed intake by ruminants, with special reference to the kinetics of rumen digestion.
(1994) Pienaar, Johannes Petrus.; Van Ryssen, Jannes Bernardus Jansen.
The aim of these studies was to examine the factors which determine voluntary feed intake and feed quality in ruminants. In the first experiments, the concepts of ruminal digestion kinetics were conceptualised and measured in animals. These concepts were applied practically in feed evaluation studies which followed. In vivo studies on alkali treated wheat straw explained why voluntary intake of ruminants increased when roughages are treated with alkali. The effect of washing the treated feed to remove excess sodium was also studied. The explanation was found in terms of ruminal digestion kinetics, showing that the mean rate of digestion was not changed, but chemical treatment improved the potential digestibility, thereby increasing the active pool size in the rumen which resulted in a faster clearance rate from the rumen. A study of the effect of starch fermentation on the kinetics of roughage fermentation in the rumen, revealed that the fermentation of different diets were affected in a different manner. The paramount factor was found to be a reduced rate of forage fermentation in the presence of starch fermentation in the rumen. A study of Pennisetum clandestinum revealed the reasons why animal performance on kikuyu pasture is often lower than what would be expected from the digestibility and chemical composition of the material. It was shown that a high soluble nitrogen content of the material was the most likely reason for low voluntary intakes, low ruminal fill and therefore poor animal performance on lush kikuyu pasture. A method was developed by which the concepts of ruminal digestion kinetics (MRT method) are used to determine voluntary feed intake with grazing animals. The method gave a mean intake that was similar to the mean obtained when intake was calculated from faecal collections, but had the advantage of a clearer pattern of intake. The accuracy obtained when using the MRT method to estimate voluntary feed intake was confirmed in a second experiment where actual intakes were known, and predicted intake was very close to actual intake. Indirect methods were developed by which two important determinants of voluntary intakes, i.e. rate and extent of digestion may be estimated. The Tilley & Terry in vitro method was adapted to allow the estimation of fermentation rates from rates of gas production. Digestion rates obtained with in vitro gas production agreed well with in sacco estimates. In vivo digestion rates were much slower than those obtained in vitro or in sacco. This discrepancy is yet unexplained, and is in contrast with the results of a previous experiment where in sacco and in vivo results were in good agreement. Increasing the mean particle size of the fennenting forages resulted in a small but statistically significant decrease in fennentation rate. Stirring the fennentation vessels did not have any positive effect on fennentation rate. Total volume of gas produced was not a good indicator of in vitro digestibility because gas production measures ruminal digestion, while in vitro digestibility includes both a ruminal and an acid pepsin phase. The rate of in vitro gas production, as measured by pressure changes in the fennentation vessels, is a practical method that was easily automated by using a data logger. The automated measurement of rate and ex'tent of digestion allows their inclusion into routine analyses for feed evaluation and the results obtained so far indicate that the system is sufficiently accurate to give useful estimates of voluntary feed intake and animal production.
A description of the genotype of pigs using simulation modelling.
(1996) Ferguson, Neil Stuart.; Gous, Robert Mervyn.
No abstract available.
Improving calving rates in Afrikaner cattle.
(1997) Lishman, Arthur William.; Gous, Robert Mervyn.
No abstract available.
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.
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.

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