Characteristics of digestion of linted and lint-free cottonseed in diets for feedlot cattle.

Eight Holstein steers (439 kg) with "T" cannulas in the rumen and proximal duodenum were used to evaluate the characteristics of digestion of Pima cottonseed. Treatments consisted of a basal growing-finishing diet containing (DM basis) 1) 15% tapioca, 2) 15% whole linted cottonseed (Delta Pine 61, DP); 3) 15% whole lint-free cottonseed (Pima, PW), and 4) 15% ground Pima cottonseed (PG). Substitution of tapioca with cottonseed decreased (P < .05) ruminal and total tract digestion of OM (10.8 and 3.5%, respectively). Net ruminal microbial N synthesis was also lower (20.5%, P < .10) with cottonseed supplementation. The greater reductions occurred with DP and PG. Characteristics of ruminal and total tract digestion of OM and N were similar for DP and PG. Grinding Pima cottonseed increased ruminal digestion of OM (13%; P < .05) and feed N (18.1%; P < .10). Ruminal digestibility of N in DP, PW, and PG averaged 50.0, 49.4, and 59.3%, respectively. Postruminal digestion of lipid was similar (P > .10) across cottonseed treatments, averaging 76.9%. The comparative DE value of DP, PW, and PG were 4.13, 3.20, and 3.80 Mcal/kg, respectively. It is concluded that the energy value of lint-free Pima cottonseed is similar to that of linted varieties provided that it is ground before feeding. However, grinding will increase ruminal N degradability 20%. Furthermore, depending on the level of incorporation in the diet, grinding Pima cottonseed may decrease ruminal microbial growth and net ruminal protein efficiency.