Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 151-159.

Thesis (M.S.)--University of Wisconsin--Madison, 1940. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 20-21).

Thesis (M.S.)--University of Kentucky, 2006. / Title from document title page (viewed on August 22, 2006). Document formatted into pages; contains: x, 99 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 90-98).

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 87-95). Also available on the Internet.

Thesis (Ph. D.)--Oklahoma State University, 2006. / Vita. Includes bibliographical references (p. 174-194).

Thesis (M. Med. Sc.)--University of Hong Kong, 2006.

No description available.

Protein utilization was investigated in the chinchilla from birth to post-weaning by studying three important stages of growth and nutritional adaptation, occurring at birth, weaning, and in adult life. The first area of study was centered on the pre-colostral chinchilla, a period which in many species is accompanied by absorption of intact proteins and immunoglobulins. immunoglobulins of the blood sera from birth to post-weaning were quantitated by polyacrylamide disc gel electrophoresis. The levels of immunoglobulins did not correlate with pancreatic enzyme or inhibitory levels in any way so as to show a relationship between inhibited enzyme levels and the amount of immunoglobulin absorbed into the blood stream. Trypsin and chymotrypsin inhibitors, assayed spectrophotometri cally, were not appreciable in the pancreatic homogenate from the young chinchilla tested. The study of adaptation can be based on the assumption that at different stages of growth, the chinchilla utilizes the proteins of its diet to different extents. This is in accordance with the change in level of protein between its first diet of maternal milk and then its secondary diet of roughage. in order to verify this assumption, pancreatic protease activity, of trypsin and chymotrypsin, was studied in seventeen chinchilla from birth to post-weaning. Homogenates of the pancreas, assayed spectrophotometrically, were used to monitor the enzymatic activity. Though not significantly different for the respective age groups, trypsin and. chymotrypsin levels tended to be highest at birth, dropping at about day three to day eight and then rising slightly at about six weeks of age where the values leveled off. The third area of study was the juvenile and adult adjustment to various rations. in this case, five rations varied in protein levels, ranging from a low protein level (11.2%) to a relatively high protein level (24.5%). Pancreatic trypsin and chymotrypsin levels were investigated to determine if pancreatic protease would respond to the level of protein in the diet. Again, enzyme levels were not significantly different between diets, but there was a tendency for the higher protein diets to result in higher enzyme values. / Land and Food Systems, Faculty of / Graduate

The growth of weanling rats receiving varying levels of methionine plus cystine in barley-based diets showed that 0.23-0.40% dry matter (DM) basis levels could not support optimal growth. No significant differences were detected in carcass composition or growth of rats receiving 0.45-0.70% DM methionine plus cystine dietary levels when either the cystine level was held constant at 0.20% DM in all diets or the methionine:cystine ratio was held constant at 2:1 and 1:1 in all diets. When either the dietary cystine concentration was held constant at 0.20% DM or the methionine:cystine ratio was held constant at 2:1 in all diets, the results indicated that cystathionine synthase activity was constant between 0.35 and 0.50% DM dietary methionine plus cystine. The activity of the enzyme was then inhibited, reaching minimum activity at the 0.60% DM dietary methionine plus cystine level. Thereafter, the activity increased to levels higher than the activity levels obtained between 0.35 and 0.50% DM dietary methionine plus cystine levels. These results indicate that 0.50% DM dietary methionine plus cystine is the limit for normal methionine metabolism. When either the dietary cystine concentration was held constant at 0.20% DM or the methionine:cystine ratio was held constant at 2:1 in all diets, the activity of N⁵-methyltetra-hydrofolate-homocysteine-methyltransferase (mTHF Enz.) was constant between 0.35 and 0.50% DM methionine plus cystine. The enzyme activity then increased, reaching maximum levels at the 0.60% DM methionine plus cystine level. Thereafter the enzyme activity was inhibited to levels corresponding to activities obtained between 0.35-0.50% DM dietary methionine plus cystine. The results indicate that normal methionine metabolism occurs up to the 0.50% DM methionine plus cystine in the diet. When the methionine:cystine ratio was held constant at 1:1 in all diets in which the methionine plus cystine concentration varied between 0.35 and 0.70% DM, cystathionine synthase activity did not respond to the varying levels of methionine plus cystine, whereas mTHF Enz. activity was inhibited progressively with increasing levels of dietary methionine plus cystine. The same results showed that increasing the dietary serine level from 0.38 to 0.58% DM depressed feed intake and the activities of both cystathionine synthase and mTHF Enz. in rats fed the 0.35-0.70% DM dietary methionine plus cystine range. The interaction between choline and methionine plus cystine when the methionine: cystine ratio was held at 1:1 in all diets showed that the 1200 mg choline chloride/kg DM diet inhibited mTHF Enz. activity and activated cystathionine synthase more than the 1000 mg choline chloride/kg DM diet. The pig trial, in which gilts were fed barley-based diets containing varying levels of methionine plus cystine, showed that the change in urinary urea-nitrogen excretion of pigs on test diets from the positive control diet, could be used as an indicator of methionine plus cystine requirements for optimal growth. Using this parameter, the requirement for methionine plus cystine for the 32.6±0.6 kg gilt was 0.55% DM on barley-based diets where cystine was held constant at 0.20% DM level. / Land and Food Systems, Faculty of / Graduate

The interaction between dietary crude protein and amino acid levels in weaner pigs in an antibiotic-free environment with or without Bacillus amyloliquefaciens supplementation Natasha van Niekerk High crude protein (CP) diets cause a myriad of digestive problems in weaner pigs due to incomplete digestion. This is caused by an immature digestive system at weaning. These problems present themselves as increased diarrhoea and reduced growth performance in weaner pigs. Many of the negative consequences could in the past be rectified through the use of antibiotic growth promoters (AGPs). However, AGPs are becoming more closely scrutinised by the general public and government officials and it is therefore imperative that alternative feed additives and dietary strategies are explored so that weaner pig performance is not impaired in the face of AGP bans. The effect of a 3% dietary CP reduction and 10% elevation of lysine, methionine, threonine, tryptophan and valine and/or Bacillus amyloliquefaciens was investigated in weaner pigs of 28 days old. The experiment was performed on 162 pigs with six dietary treatments; comprising of two CP levels (21% or 18% in the pre-starter diets and 18% or 15% in the starter diets), two amino acid levels (recommended amino acid level or elevated by 10%) and with or without the supplementation of a probiotic additive (Bacillus amyloliquefaciens). The total trial period was 42 days, divided into a pre-starter phase and starter phase, both of 21 days each. Growth performance and faecal score was measured for the entire trial period. In addition, after 21 days of the trial, 54 pigs were humanely euthanised to determine the gut health effects of the dietary treatments. Crude protein level resulted in significant effects on body weight (BW), average daily gain (ADG) and gain to feed ratio (G: F) in both the pre-starter and starter phase. The pigs consuming the HP diets had increased (p <0.05) BW at day 7, 14, 21, 28 and 35, and higher ADG (p <0.01) between days 7-14 and 7-21. In addition, high CP diets resulted in increased (p <0.05) G: F in the periods 7-14, 7-21, 21-42 and 7-42. This was due to the negative impact incurred as a result of deficiencies in certain essential AA and the standard ileal digestible (SID) Lys to CP ratio (SID Lys: CP) of 6.9% being exceeded when CP was reduced, and supplemental AA increased. The reduction in CP resulted in improved faecal scores. The supplementation of the probiotic did not result in any significant effects on performance but did exert a positive synergistic effect with the low CP diet on gut health, as observed through improved faecal score. Ileal villi height was significantly increased in high CP diets, possibly indicative of increased nutrient availability in the high CP diets. Crypt depth was also increased in the high CP diets, indicative of increased cell proliferation. There were no significant dietary effects on the pH and ammonia content of caecal digesta, or the presence and enumeration of Salmonella and Escherichia coli (E. coli) in ileal and caecal digesta. Interestingly, the supplementation of the probiotic increased the relative liver weights of the pre-starter pigs. Results of the study suggest that in order for the strategy of reducing CP in weaner pig diets to be successful, no deficiencies in essential or non-essential amino acids should be present. In addition, low CP diets in conjunction with a probiotic can improve faecal scores of weaner pigs, providing an effective solution to replacing AGPs. / Dissertation (MSc)--University of Pretoria, 2020. / Evonik Nutrition & Care GmbH / Animal and Wildlife Sciences / MSc (Agric) Animal Nutrition / Unrestricted