True intestinal digestibility of amino acids of forage and browse legumes in cattle

Abstract

The mobile bag technique was used to estimate the true intestinal digestibility of amino acids in Vigna uncuiculata (cowpea), Desmodium uncinatum (silverleaf desmodium) and Brachystegia spiciformis (Musasa) tree foliage. Three multiparous, lactating, mature Holstein x Mashona crossbred dairy cows fitted surgically with ruminal cannulae and T-piece duodenal cannulae were used. The intestinal disappearance of total, indispensible and dispensable amino acids across the legumes after pre-incubation in the rumen for 12, 24 and 48 h was estimated. Silverleaf desmodium had the highest concentration (P ≪ 0.05) of total, indispensable and dispensable amino acids Aspartic acid concentration was more than double (P ≪ 0.05) in si1lverleaf desmodium compared to that in cowpea. There was an interaction (P ≪ 0.01) between the feed type and the pre-rumen incubation time on the disappearance of total amino acids (TAA), indispensable amino acids (IAA) and dispensable amino acids (DAA) in the intestines. The intestinal disappearance of TAA, IAA and DAA was largest in Cowpea after incubation in the rumen for 48 h. Overall, these results suggest that Musasa foliage and silverleaf desmodium provide less rumen degradable nitrogen but more rumen undegraded dietary nitrogen to the intestines than cowpea.