Call number: LD2668 .T4 1952 S96 / Master of Science

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

The lipid composition of swine is characteristic of the species and is also a reflection of their dietary history. Other investigators have established that the physical properties and composition of swine depot fat may be altered by variation of the dietary lipid. Dietary regimens employing vegetable oil-bearing materials and their effect on meat quality has received the attention of animal nutritionists for a considerable period. Less is known about the nutritive value of the more highly unsaturated lipids, such as fish oils, and their effect on the lipid composition of swine tissues. Even less is known about the fate of oxidized fish oil lipids in swine rations. This research had for its purpose the investigation of the fate in swine of the dietary marine lipid, menhaden oil, and its effect on composition of depot lipids. The state of autoxidation of the oil and the effect of certain antioxidants on the fatty acid composition of swine was determined. Growth studies on swine were made using menhaden oil of various oxidation states as the dietary lipid. The effect of antioxidants, ∝-tocopherol acetate and ethoxyquin, was also investigated. At the conclusion of the diet trials, tissue samples, representing the five dietary regimens, were removed for analysis. The fatty tissues examined were outer back fat, inner back fat, and kidney fat. Samples of liver tissue for lipid analysis were also taken. The lipids from the respective tissues were extracted and interesterified with methanol to yield the methyl esters of the fatty acids. Hydrogenation of the unsaturated methyl esters for chain length confirmation was carried out. Qualitative and quantitative gas-liquid chromatographic analysis of the unhydrogenated and hydrogenated methyl esters of the fatty acids were performed on diethylene glycol succinate column. The results of these investigations showed that a particular dietary fatty acid can be selectively deposited in animal tissues. Long chain polyunsaturated fatty acids of menhaden oil, such as 20:5, 22:5, 22:6 were sparsely deposited in adipose tissues. The depot fat composition showed a mixture of characteristic menhaden oil fatty acids with the typical fat synthesized by swine. Fatty acid composition of tissue from swine fed oxidized menhaden oil with and without antioxidants showed very similar fatty acid composition as those fed fresh menhaden oil. The results of this investigation supported the beneficial effect of vitamin E (∝-tocopherol acetate) and ethoxyquin as in vivo antioxidants. / Graduation date: 1964

I consider two types of foraging situations. In the first type, the forager knows the location and quality of no more than one food item or habitat at a time. I call this myopic foraging. In the second situation, the forager may know the location and quality of more than one food item or habitat at a time. I call this periscopic foraging. I develop theoretically both models and the predictions generated by each. Myopic models predict that foragers should have a so-called "bang-bang" control with respect to the choice of food types. Periscopic models predict that foragers will have a continuous control with respect to the choice of food types. I experimentally tested for the presence of each type of control in a field study that employed hummingbirds feeding on artificial resources. As predicted by the theory, the transition of behavior from picky to opportunistic was significantly sharper for the myopic than for the periscopic foragers. Furthermore, theory predicts that there should be some range of relative values of the rich and poor food types over which the myopic foragers are opportunistic, while the periscopic foragers exhibit a partial preference. This prediction was supported by the data. I predicted that the partial preferences of periscopic foragers would result from the hummingbirds exploiting those poor quality feeders which were located nearest to the best foraging path among rich feeders. The data supported this prediction. Periscopic foragers also performed as predicted by becoming more selective on rich feeders as the densities of both rich and poor feeders increased. I developed a model of optimal sampling behavior that hypothesized birds have evolved in an environment of exploitative competition. The model predicted a rule of departure from a resource patch that depended on the presence or absence of nectar in a sampled as well as the expected quality of the nectar. Hummingbirds performed according to the model's predictions.

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The aim of this research was, first to test the suitability of different seaweeds and formulated feeds as food for post-weaning juvenile South African abalone and secondly, to test the effects of basket design on the growth of grow-out juvenile abalone in both flow-through and re-circulation systems.

The objectives of this study in the Nakuru District of the Kenyan Highlands, the major milk sources for the Nairobi milk market, were to evaluate current dairy cattle rearing and feeding practices, and suggest efficient feeding management strategies on large and small-scale commercial dairy farms. 139 small-scale farms with 738 dairy cows were surveyed and 6 large-scale dairy farms with 4379 dairy cattle. On the small farms, high mortality rates, cost of AI, and disease were the major causes of poor reproduction leading to a lack of replacement stock. Feeding systems used were: 24% free grazing system, 33% semi-zero grazing, 40% zero grazing, and 3% rotational grazing, but limited feeds were available – crops and feed crop residues, cut grass on the roadside, neighbouring farms with some purchased hay and straws in the dry season. After weaning, feed supplements were rarely given to calves, priority being given to milking cows, explaining the few replacement stock kept and their high mortality. The six large scale farms were from 200 to 3500 acres with milk production, cereal crops, fodder crops, the scale of replacement dairy stock and hay to other dairy farms the main activities with land allocated 65% to livestock, 20% to cash crops (Barley and Wheat), 10% to fodder crops and 5% to other land-uses. Replacement heifers for sale were insufficient to meet demands from small-scale farms. Grazing systems were mainly extensive with supplements fed at milking.  All the farms depended on planted forage grasses, mainly: Rhodes grass, Star grass, Sudan grass and Kikuyu grass. Calf mortality rate (10-18 %) was high caused mostly by respiratory diseases and East Coast Fever. Extended age at first calving (>31.8 ± 4.5 months), long calving intervals (> 406 days) and low average milk yields (6.81/day ± 3.9) for all breeds, occurred. Production and reproductive performances needs to be addressed by proper nutrition. Suitable pasture grasses, legumes and fodder crops not currently being used have been identified as potential options to complement the existing pasture. Among these are: Guinea grass (panicum maximum), Cynodon dactylon, Buffel grass (Cenchrus ciliaris), Naivasha star grass (Cynodon plectostachyus) and Rhodesian star grass (Setaria sphacelata). Other studies examining supplementation of animals on low quality pastures with the above feeds resulted in increased body weights and milk yields. The greatest potential seems to be supplementing with home-grown proteinaceous feedstuffs such as Leucaena leucocephala, Calliandra, Sesbania or food crop residues like groundnut, cassava, sweet potato vines or pigeon-pea leaves and stems. Farmers could increase their pasture land productivity by establishing fodder grass, fodder shrubs and food crops as intercropping, hedgerows and along contour bands.

Call number: LD2668 .T4 1952 B7 / Master of Science