Apparent Digestibility of Amino Acids and Nitrogen in Three Cottonseed Meals and one Soybean Meal

The digestibilities of amino acids and N in commercially-processed direct solvent (DS) and screwpress (SP) cottonseed meals, laboratory processed glandless (GL) cottonseed meal and 44% crude protein soybean meal (SBM) were determined at the end of the small intestine and over the total digestive tract of finishing pigs. The trial was conducted as a 4 × 4 Latin square with four littermate barrows fitted with simple T-cannulas approximately 15 cm proximal to the ileocecal valve. Ileal digesta were channeled out of the cannula by inflation of a 30-ml Foley catheter in the intestinal lumen caudal to the T-cannula. Digestibilities of N and the 10 essential amino acids (EAA) at the end of the small intestine and over the total digestive tract were higher (P<.05) with GL and SBM than with DS and SP. At the end of the small intestine, GL had higher (P<.05) N, arginine, methionine and valine digestibilities than did SBM, and SP had higher (P<.05) arginine and phenylalanine digestibilities than did DS. Over the total digestive tract GL had higher (P<.05) digestibilities of N, arginine, histidine, methionine, phenylalanine and valine than did SBM, and SP had higher (P<.05) digestibilities of all EAA, except lysine, methionine and tryptophan, than did DS. Lysine was the least digestible of the EAA in DS (61.7%) and SP (64.0%) at the end of the small intestine; in contrast, it was highly digestible in GL (88.5%) and SBM (87.1%). This wide difference indicates that diets containing commercial cottonseed meals may need higher total lysine levels to achieve the performance obtained with SBM-supplemented diets. A comparison of digestibilities at the end of the small intestine and over the total digestive track indicated a net loss of most amino acids in the large intestine.