Thesis (M.Tech.: Biotechnology)-Dept. of Biotechnology, Durban University of Technology, 2007 v, 125 leaves / Ruminants diets in most developing countries are based on fibrous feeds, mainly mature pastures and crop residues. These feeds are unbalanced and particularly deficient in protein, minerals and vitamins and are highly lignified with low digestibility. These characteristics result in low intake and productivity and only approximately 40% of energy in forage becomes available to the animal. Enzymes can be used as biological tool to enhance digestion through the action of cellulase, hemicellulase and lignase enzymes resulting in improved meat, milk and wool production. The development of feed additives holds great promise for the improvement of livestock growth and yield for both large commercial and smaller subsistence farmers. The aim of this study was to develop optimal media for the production of lignocellulolytic enzymes (laccases, xylanases, and cellulases) and to evaluate the application of these enzymes to improve the nutritional digestibility of high fibre feedstocks, such as veld grass.

In traditional forage breeding programmes, breeders have spent decades improving the agronomic characteristics of grasses, such as herbage yield, persistence and resistance to diseases, without considering the nutrient requirements of the grazing animal. In an attempt to improve the nutritive value of Italian ryegrass, which is widely utilised for intensive dairy, lamb and beef production in South Africa, Enhancer ryegrass was developed from predominantly Italian types of Lolium multiflorum, with a minor Westerwolds component, by selecting for a higher concentration of total nonstructural carbohydrate (TNC) and lower moisture content than that currently available in commercial cultivars. The nutritional value of Enhancer was compared with Midmar ryegrass in a controlled environment study and in a grazing trial with weaned lambs; and with Dargle ryegrass in a grazing trial with Holstein dairy cows. Neutral detergent fibre, acid detergent fibre, lignin, nitrogenous compounds, mineral content and in vitro digestibility were also investigated as parameters of nutritive value. The anatomical features of Enhancer and Midmar were studied to determine possible structural differences. Weaned lambs grazed Enhancer and Midmar in an eight-paddock rotational grazing system, with 3.5 days spent in each paddock, allowing a 24.5 day regrowth period for the pastures. Holstein dairy cows grazed Enhancer and Dargle which were established on 16 and 19 hectare pastures, respectively. The n-alkane technique was used to estimate dry matter intake (DMI) in both grazing trials. Results from the controlled environment study suggest that the differences in the dry matter and TNC concentration of Enhancer are not positively linked to anti-quality factors associated with forage species, but can be attributed to genetic differences between the two grasses. Despite the significantly higher (P < 0.01) DMI of weaned lambs grazing Midmar compared with Enhancer, the lambs on Enhancer outperformed those on Midmar in terms of liveweight gain and carcass quality. The superior animal performance on Enhancer is likely due to an improvement in the readily digestible energy to protein ratio as a result of its significantly higher (P < 0.001) concentration of TNC compared with Midmar. Milk yield for cows grazing Enhancer in period 1 of the cross-over study was significantly higher (P < 0.05) than for cows grazing Dargle, despite the significantly lower (P < 0.05) DMI of animals on Enhancer. The higher TNC concentration relative to the true protein content of Enhancer would suggest that the protein metabolism in the rumen can be enhanced. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.

Experiments were conducted to examine the role of dietary selenium (Se) and changes in antioxidant capacity during DMBA-induced mammary carcinogenesis. Weanling rats were fed graded amounts of Se in an AIN-76 diet, modified to approximate the amount and type of dietary fat consumed in Canada. Animals fed 3-4 ppm Se had a reduced tumor incidence but there was evidence of chronic Se toxicity. Low Se did not elevate tumor incidence. Thus, supplemental dietary Se did not offer any protection in reducing the incidence of cancer when rats were fed a diet representative of North American intakes of fat. Blood GSHPx activity was elevated in rats that remained free of tumors (NT group) compared to animals that would eventually develop tumors (WT group). SOD activity was reduced in WT and NT rats, but appeared to be related to carcinogen administration. These differences were observed before tumor development and over a wide range of Se intakes. WT rats excreted more $ sp{75}$Se compared to both control and NT rats. These changes, however, were not reflected in elevated lipid peroxidation. Thus, one of the protective mechanisms during carcinogenesis may be the capacity of the animal to elevate GSHPx activity.

This study examined the effects of early nutrition or, the body weight and adipose tissue characteristics of Sprague-Dawley rats. Different levels of caloric intake during the pre-weaning phase were achieved by manipulation of litter size. Immediately after birth, pups were redistributed into large (15-18 pups), control (1O pups), or small (4 pups) litters. Males from small litters demonstrated an increase in body weight and adipocyte, number (K.05), but this difference was not seen in the females. Litter size had no effect on adipc"cyte size or percent body fat. The effect of caloric restriction during the post-weaning phase was also examined. This was done by pair-feeding one-half of the rats raised in small litters to those raised in large litters for a period of 5 weeks. After ad libitum feeding was resumed, the pair-fed group demonstrated an increase "in adipocyte size which resulted in an increased level of fatness W.05). The results of this experiment demonstrate that the consequences of early nutrition are dependent on when it is undertaken, and suggest that sex hormones are involved in modulating these effects.

In a 28-day dietary study, Lumbricus terrestris were placed in one quart containers with soil and offered either corn (Zea mays L.), soybean (Glycine max L. Merr.) or alfalfa (Medicago sativa) leaves, corn leaves treated with a 1:1 solution of 28% N fertilizer and deionized water, corn or soybean stalks, or no addition. The worms were weighed initially and after 28 days to determine biomass production, which was used for determining food quality. Worms exhibited large weight gains when fed alfalfa or soybean leaves, intermediate weight gains when fed corn leaves treated with N, and little or no gains for the remainder of treatments. N content of the tissues was positively correlated to biomass production. These results support the hypothesis that earthworm growth is determined by food quality, particularly N content. / Department of Natural Resources

Scottish red deer (Cervus elaphus scoticus) are smaller in size and mature later than many continental subspecies. Previous investigations at the Rowett Institute have shown that when Scottish red deer are fed well they grow almost as large as European deer, so the differences between subspecies appear principally determined by the environment. To test this, one group of 6 stag calves was fed to appetite while a second group of 6 was offered 70% as much (on a metabolic body weight basis) during the winter and both groups fed to appetite during the following summer. After the first winter the restricted group were lighter and skeletally smaller than the unrestricted group. Despite compensatory growth during the summer significant differences in weight and size remained at the end of the period of feeding to appetite. This pattern was repeated during the second and third years of the study, Plane of nutrition bad little effect on size and composition of antlers but had profound effects on the timing of growth of the first antlers. Although the restricted stags were less fat than the unrestricted stags both groups showed the same relationship of fat content of the body to empty body weight. The restricted plane of nutrition delayed the growth and moult of wool and hair but did not affect length of either. The restricted plane of nutrition exerted only slight effects on levels of testosterone, oestradiol 17 beta,prolaotin and thyroriue and no effect on the timing of their cycles. A field study on the effect of winter undernutrition on stag calves at Glensaugh Deer Farm gave similar results. Cycles of body weight and food intake were shown to be of smalleramplitude in captive hinds than stage. Superior cervical ganglioneotomy of Soay rams diminished the amplitude of cycles of food intake and growth as much as cycles of reproduction but failed to abolish either.

The problem of reduced appetite in ruminants fed silages persists but the factors responsible for reduced intake of silage have not been elucidated. This study was conducted with the objective of testing the hypothesis that ammonia loading in ruminants could suppress appetite. In a 5 x 5 latin square design, sheep were fed alfalfa silage (S), fresh alfalfa (FA), and FA with added equimolar amounts (450 mmol. kg$ sp{-1}$ feed DM) of NH$ sb4$Cl, NH$ sb4$HCO$ sb3$ and urea; the latter was infused directly into the rumen. The silage had a DM content of 33.1%, pH 4.4, and a lactic acid content of 4.3% of DM. Unfermented herbage had a pH of 5.5 and lactic acid content of 0.2% of DM. Digestibility of organic matter (OMD) exceeded 70% for both S and FA. Organic matter intake (OMI), digestible organic matter intake (DOMI), concentration of rumen NH$ sb3$, rumen pH, osmolality and volatile fatty acids (VFAs) did not differ (P $>$ 0.05) among treatment groups. The lack of differences among treatments may have been as a result of a failure to accentuate qualitative and quantitative differences between the FA and S and to raise ammonia in the rumen and peripheral blood to levels that could alter appetite.

Three experiments were conducted to characterize the fate of B-vitamins in the gastrointestinal tract of dairy cows. Experiment 1 was undertaken to verify if differences among published studies could be explained by methods of collection and preparation of ruminal fluid, using four ruminally cannulated non-lactating Holstein cows. Acidification of fresh ruminal fluid, causing the lysis of bacterial cells, yielded higher B-vitamin concentrations than differential centrifugation, while the method of collection used did not have an important impact. Results suggested that most of the vitamins are present in the bacterial fractions, and that only limited amounts are present in the surrounding fluid. Experiment 2 looked at the vitamin concentrations in ruminal bacterial fractions and particle-free fluid as influenced by diet composition. Six lactating ruminally cannulated Holstein cows were used in a cross-over design, and the diets were formulated to have forage to concentrate ratios of 60:40 (high-forage) and 40:60 (low-forage). B-vitamins were present mainly in the bacterial fractions of the rumen, with greater effects of the forage to concentrate ratio on vitamin concentrations in the bacteria associated to the solid fraction than on those present in the liquid portion of the rumen. These results strongly suggested that ruminal B-vitamin synthesis is influenced by the forage to concentrate ratio. Experiment 3 investigated the fate of supplementary B-vitamins, using four cows equipped with cannulae in the rumen, the proximal duodenum and the distal ileum. Extensive losses of dietary supplements appeared prior to the duodenum for all vitamins, but intestinal disappearance rates of most vitamins were increased by supplementation.

Thesis (PhD)--University of South Australia, 1999

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