The performance of broiler chicks fed diets containing extruded cottonseed meal supplemented with lysine

Department of Poultry Science, University of Georgia, Athens 30602, USA.

Three experiments were conducted to test the hypothesis that extruding cottonseed meal (CSM) with supplemental lysine improves its feeding value by detoxifying gossypol. The performance of 1-wk-old straight-run Peterson x Arbor Acres broiler chicks fed diets containing 20% feed-grade or extruded CSM was compared with that of control chicks fed corn and soybean meal-based broiler rations. All diets were formulated to meet minimum NRC requirements. Lysine levels were adjusted by addition of synthetic lysine at rates of 0.5 to 2.0% of the protein in CSM. In all experiments, weight gain, feed intake, and feed conversion ratio (FCR) of broilers at 21 d were significantly affected by the diets. Feeding feed-grade and extruded CSM resulted in decreased body weight gain, increased feed intake, and inefficient feed utilization. When 2% lysine was added to feed-grade or extruded CSM, the body weight gains of chicks were not significantly different from those fed the control diet. The FCR of chicks fed feed-grade and extruded CSM plus 2% lysine at 21 d was significantly better than that of chicks fed feed-grade or extruded CSM alone. Abdominal fat pads (as a percentage of body weight) were significantly increased by the inclusion of CSM with or without the addition of lysine (P < or = 0.019). Liver, spleen, and heart weights were not affected by the presence of 20% CSM in the diet. The effects of CSM on plasma iron level was not consistent. Only in Experiment 1 did CSM cause a significant reduction in plasma iron. The hemoglobin contents and hematocrit values of blood from chicks fed diets with 20% CSM were not significantly different from those of the controls. The extrusion process reduced the free gossypol in CSM, but the total gossypol level was not changed, and chick performance was not improved. However, this study shows that, with adequate supplemental lysine, CSM can be used in broiler diets without a reduction in performance.

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