EFFECT OF WHOLE COTTONSEED, GOSSYPOL, AND RUMINALLY PROTECTED LYSINE SUPPLEMENTATION ON MILK-YIELD AND COMPOSITION

To determine whether the gossypol content of the diet affected availab ility of dietary Lys, 4 cows with ruminal and duodenal cannulas and 16 intact cows in early lactation were assigned to diets containing eith er glanded cottonseed, glanded cottonseed plus 15 g/d of ruminally pro tected Lys, glandless cottonseed, or glandless cottonseed plus 15 gld of ruminally protected Lys. The experimental design was a 4 x 4 Latin square design with 3-wk experimental periods. Gossypol concentrations in plasma were lower when cows were fed glandless cottonseed. Lysine s upplementation increased the flow and percentage of Lys in duodenal di gesta and increased the concentration of Lys in plasma. Neither type o f cottonseed nor Lys supplementation affected dry matter intake. Yield s of milk and fat-corrected milk from cannulated cows were not affecte d by diet, but yields from intact cows were increased by Lys supplemen tation. For both cannulated and intact cows, Lys supplementation incre ased the percentage of milk protein, and milk protein yield was increa sed by Lys in intact cows. Dietary gossypol did not affect the respons e to Lys, indicating that dietary gossypol had little or no effect on the availability of Lys for dairy cows.