Rumen degradability and post-ruminal digestion of dry matter, nitrogen and amino acids in three tropical forage legumes estimated by the mobile nylon bag technique

Abstract

The ruminal degradability and intestinal digestibility of dry matter (DM), nitrogen (N) and amino acids (AA) in whole plants of tropical forage legumes were estimated in three rumen and duodenal cannulated non-lactating Holstein/Friesian cows using the mobile nylon bag method. The legume samples were incubated in the rumen for 12, 24 and 48 h. After rumen incubation, the mobile bags were pre-incubated in pepsin–HCl solution before inserting into the duodenum and recovering in the faeces. Rumen DM degradabilities of cassia and of siratro were greater than that of lablab and increased with increasing rumen incubation time. The post-ruminal digestibility of undegraded DM was not different between the legumes. Similarly, N degradability was not different among the three legumes after similar incubation periods. However, the intestinal digestibility coefficients of rumen undegradable N in cassia and siratro were greater than that of lablab. The digestibility of total amino acids varied between 0.346 and 0.771. The digestibility coefficients of essential amino acids and non-essential amino acids followed a trend similar to that of total amino acids. Siratro showed the highest digestibilities of individual amino acids, total amino acids and nitrogen with cassia being intermediate and lablab the least. These results indicate that undegraded legume proteins differ as sources of absorbable amino acids in the small intestines.