| dc.description.abstract |
Three samples of cottonseed meal were substituted for soyabean meal on an isonitrogenous basis in broiler starter diets. With adequate supplementation of methionine and lysine, diets containing 31.3 per cent of cottonseed meal were associated with slightly inferior performance. Subsequently, a further three samples of screwpressed cottonseed meal produced by different defined processing conditions were evaluated by chemical tests and by a broiler growth experiment. The proportion of lysine chemically unavailable was 15 per cent for a mildly heat-treated cottonseed meal, and 38 per cent for an over-heated sample. When cottonseed supplied 14 per cent of the 20 per cent dietary crude protein, growth was depressed compared with soyabean meal diets. The depression was minimised if the total dietary lysine level was elevated to 1.3 per cent. However, feed conversion efficiency was inferior on all cottonseed diets. When supplemented comprehensively with amino acids, a cottonseed meal processed with prolonged cooking had a 'Total Protein Efficiency' value of 2.13, whereas a superior cottonseed meal processed with less cooking recorded 2.59 and soyabean meal, 2.97. Extra lysine supplementation improved the total protein efficiency values for the cottonseed meals, in particular the over-heated meal recorded 2.55. |
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