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Call number: LD2668 .T4 1966 N833 / Master of Science

A dietary level of Aroclor 1254 (100 ppm) was fed to rainbow trout (Salmo gairdneri) for 15 weeks to determine the effects on hepatic microsomal enzyme induction. Fish were also fed combined polychlorinated biphenyl (PCB) (100 ppm) and cyclopropene fatty acids (CPFA) (50 ppm) to determine the effects on mixed function oxidase (MFO) induction. Dietary PCBs markedly induced the microsomal activities of 7-ethoxyresorufin O-deethylase, 7-ethoxy-coumarin O-deethylase, and benzo(a)-pyrene monooxygenase. Ethoxyresorufin O-deethylase activity continued to increase to a level 77-fold higher than control at week 15. Ethoxycoumarin O-deethylase and benzo(a)-pyrene monooxygenase activities increased to 7.1-fold and 48-fold over control at week 9 and then slightly decreased to 6.8-fold and 45-fold over control at week 15, respectively. Cytochrome P450 values remained approximately 2-fold above controls from week 5 through week 15. At weeks 1 and 3, cytochrome P450 levels were not significantly different from control. Ethoxyresorufin O-deethylase, ethoxycoumarin O-deethylase, and benzo(a)pyrene monooxygenase activities in the combined PCB and CPFA-fed trout were significantly higher than in controls and CPFA-fed fish, and significantly lower than in PCB-fed fish. There was no significant difference in cytochrome P450 levels after week 5. This is the first time dietary PCBs have been shown to induce the MFC system in PCB-fed rainbow trout. / Graduation date: 1980

The aflatoxins, carcinogenic and toxic mold metabolites of Aspergillus flavus, were isolated and determined in cottonseed meal and other feedstuffs. This new quantitative method uses an acetone soxhlet extraction to remove the toxins from the defatted meal. The residual triglycerides, phospholipids and pigments were removed from the acetone by filtration of the cooled solution. The aflatoxin was further isolated by evaporating the acetone and redissolving the residue in hot methanol. After cooling, the insolubles were discarded and the methanol-soluble materials taken up in chloroform. The chloroform solution was spotted on silicic acid thin layer chromatographic plates along with suitable standards. After development with 9:1 (v/v) chloroform:acetone, the chromatographic plates were examined under ultraviolet light. Complete recovery of aflatoxin, within limits of visual discrimination, was obtained by this isolation procedure as indicated by extraction efficiency and internal standard data. Twenty-five cottonseed meals were analyzed by this method and nine meals contained aflatoxin B₁ at levels from 17 to 190 parts per billion. Fluorodensitometry, a new instrumental technique, was used to compare standards and samples containing aflatoxin directly from the thin-layer chromatographic plate. This procedure eliminates the errors inherent in the visual comparison method and permits greater sensitivity and accuracy. Amounts of aflatoxin B₁ as low as 8.0 x 10⁻⁵ micrograms can be detected by this technique. The results obtained by this procedure were substantiated by duckling assay and trout feeding trials. / Graduation date: 1966

An experiment was conducted with laying hens to evaluate the effects of added lysine, methionine and tallow on laying hen performances. Twenty-four treatments were obtained as a result of supplementing the basal diets, which contained either 13.86% or 13.5% protein, with 4 levels of synthetic L-lysine Hcl and with 3 levels of DL-methionine. Each treatment was fed to 5 neplicates of four birds each for ten 28-day periods. Tallow was added at a level of 4% to the 13.5% protein diet. Significant improvements were obtained in egg production and in egg mass as a result of lysine and methionine supplementation. However, 4% added tallow significantly decreased egg production and egg mass. On the other hand, tallow exerted positive effects upon the efficiency of feed utilization only when the diets were adequate in both lysine and TSAA. Three response criteria were used to measure the daily intake of lysine and total sulfur amino acids which are methionine and cysteine (TSAA) required by laying hens; percent egg production, egg mass, and plasma free lysine and TSAA levels. The pattern of response suggested that the dietary lysine requirements were 718 and 709 mg/hen/day for egg production and egg mass respectively; and the dietary TSAA requirements were 616 and 626 mg/hen/day for egg production and egg mass respectively. Multiple regression analysis, which related the intake of these amino acids with hen performances showed numerical, but non-significant, differences than the above requirement values. Using plasma free lysine and TSAA as criteria, the requirements for lysine and TSAA obtained from regression analysis were 674.8 and 561.6 mg/hen/day respectively. Feed intakes and protein intakes were not significantly affected by either lysine or methionine supplementation. However, 4% added tallow significantly decreased feed intakes and protein intakes.

Foraging by captive individuals of three species of towhees (Pipilo:Emberizinae) was investigated to determine if patch choice was associated with critical threshold levels of foraging success. Birds were offered a choice of feeding in three litter types. Once individual preferences for litter type were determined, I reduced the amount of food (millet seed) under a preferred litter each day, while maintaining high levels under a non-preferred litter. Thus, birds experienced a declining resource gradient under their preferred litter. During the bird's initial foraging period each day, I noted number of seeds taken and number of double-scratches made in each litter type, until the bird abandoned its preferred litter and shifted to the other patch. Foraging theory assumes that patch choice is made when foraging success declines as resources decline to some threshold level. I estimated success using information potentially available for decision-making by the birds. One of four success variables, mean seeds/scratch, best conformed to the expected pattern, providing supportive evidence for the threshold assumption. The three species changed patches at species-specific thresholds. Pipilo fuscus, a foraging generalist, switched to its non-preferred litter when food levels under the preferred litter were high. Pipilo aberti and P. erythrophthalmus, two foraging specialists, foraged in their preferred litters until food levels were much lower. Optimal Foraging Theory predicts that shifts in patch use are determined by between-patch comparisons of foraging success. Timing of towhee patch changes was not consistent with between-patch comparisons. An alternative expectation theory, Status-quo Foraging, which emphasizes comparisons of within-patch success, was more consistent with observed results. The rapid patch switching shown by P. fuscus may reflect greater flexibility of this species' foraging repertoire in its natural habitat. This result suggests that foragers with imperfect knowledge may use recent past experience to make foraging decisions. Optimal Foraging Theory provided a useful null model for comparing foraging theories. Deviations from predictions indicated how more realistic hypotheses can be constructed. The nature of available information plays an increasingly important role in modeling decision-making by imperfect foragers.

Three experiments were conducted to study changes in exocrine pancreas function in relation to age, dietary fat and digestibility in poultry. In the first experiment, 120 White Leghorn and 120 Hubbard chicks were fed a basal diet with or without 5% animal fat. Total units of lipase, amylase, trypsin and chymotrypsin activities in pancreas increased linearly with age in Hubbards from 2 to 29 days, but plateaued after 16 days in Leghorns. Hubbards showed higher total pancreatic lipase, amylase, trypsin and chymotrypsin activities compared with Leghorns. Addition of 5% dietary fat significantly increased total lipase activity in pancreas, but decreased total amylase activity. Added fat had no well defined effect on total pancreatic trypsin and chymotrypsin activities. Fat digestibility in Leghorns fed the low fat diet increased significantly from 14 to 30 days of age, but not in Leghorns fed the high fat diet; while Hubbards fed both diets showed a significant decrease in fat digestibility. Fat digestibility was increased with added fat in both breeds. No direct correlation was found between nutrient digestibility and corresponding enzyme activity. In the second experiment, 80 young White Leghorn hens were fed a basal diet with or without 5% animal fat. Fat supplementation did not generally significantly affect lipase activities, but total lipase activity in pancreas decreased after 10.6 and increased after 12.7 mo in pancreata of birds fed both diets and fed the high fat diet, respectively. Fat digestibility was not affected by age, but was higher with fat supplementation. In the third experiment, 96 older White Leghorn hens were fed a basal diet with or without 5% animal fat. Total pancreatic lipase activity showed a U-shaped curve with the lowest value at 15.7 mo and increased after 15.7 mo following either natural or force molting. Fat supplementation did not significantly affect lipase activities. Amylase, trypsin and chymotrypsin activities decreased with age from 10.2 to 15.7 mo, but were increased with fat supplementation. Fat digestibility was not affected by age, but was significantly higher with fat supplementation.

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