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2. Under the same conditions including α‐tocopheryl acetate or ethoxyquin significantly improved the stability of these tissues. 相似文献
2. Each experiment involved a total of 3 888 laying pullets. Nine diets, with crude protein contents ranging from 87 to 212 g/kg, were used in the first experiment and ten diets, with protein contents ranging from 81 to 215 g/kg, in the second experiment. Diets were denned in terms of their calculated contents of essential amino acids and the same, well‐balanced amino acid profile was used at all protein contents within one experiment. Supplementary experiments were conducted to identify the limiting amino acid (s) in the experimental diets.
3. Treatments were applied for ten weeks, starting at 30 or 32 weeks of age. Average egg output on the highest protein diets was 57.0 g/bird d in the first experiment, which used White Leghorn pullets, and 53.7 g/bird d in the second experiment, which used a crossbred brown‐egg stock.
4. The response curves obtained showed diminishing returns and, in the second experiment, a clear plateau was reached. The Reading model was fitted and compared with a two‐straight‐line model and with curves derived from quadratic and inverse polynomial equations. Only the Reading model proved satisfactory for the interpretation of the data, as judged by goodness of fit and estimation of the optimum amino acid input. Although alternative models may provide a good fit when dealing with a single set of data, none of the alternatives is consistently satisfactory when considering the results of more than one experiment. 相似文献
2. Diets prepared by serial dilution of a concentrated protein mixture, well‐balanced with respect to all essential amino acids, were fed in three experiments, while in a fourth experiment, a lysine‐deficient protein mixture was used.
3. Response curves relating body‐weight gain to increasing concentrations of protein and of lysine intake are presented.
4. A table is presented from which optimum protein intakes can be calculated according to changes in input and output costs and changes in growth potential of the chickens. 相似文献
2. There were some differences between the two ages; these could largely be reconciled by considering the likely differences in the proportion of feather protein.
3. The results were compared with similar values for the chicken and goose; overall there is a striking similarity, both in absolute concentrations and relative proportions of amino acids. 相似文献
2. Addition of 10 g ascorbic acid/kg to the control diet (without excess tyrosine) produced no beneficial effects on performance. Excess dietary tyrosine caused depressions in all measures of performance.
3. Adding 0.1, 1, 10 or 20 g ascorbic acid/kg to the diet containing excess tyrosine tended to improve performance.
4. Subcutaneous injection of 50 mg ascorbic acid/bird d to chicks receiving excess tyrosine brought about a significant improvement in body‐weight gain.
5. The elevation of plasma free tyrosine caused by excess dietary tyrosine decreased as dietary ascorbic acid increased.
6. Ascorbic acid can alleviate, though not completely counteract, the adverse effect of excess dietary tyrosine. 相似文献
2. In the early stage of growth the feather shaft is held in place by cell indentations, whereas later, bridges are seen which probably hold the feather more firmly. 相似文献
2. Male broilers grew linearly up to 76 d whereas the females grew more slowly after 35 d. At 364 d the difference in live body weight was small.
3. Up to 56 d, males had a slightly higher eviscerated yield. There was no significant difference between the sexes beyond this age.
4. The proportional yield of breast muscle was variable with age, whereas that of thigh and drumstick increased with age in the male, particularly at 175 and 364 d.
5. After 35 d the proportion of skin was larger in females, whereas the gizzard as a proportion of live body weight in both sexes decreased rapidly between 21 and 76 d. Blood loss during killing was always higher in male broilers after 21 d. 相似文献
First European Symposium on Poultry Welfare. Edited by L. Yding S0RENSEN. Published by the Danish Branch of World's Poultry Science Association. 1981. 238pp. D.Kr.90. ISBN 87–88162–00–1. 相似文献