Digestibility of amino acids in protein rich tropical feeds for ruminants estimated with the mobile bag technique

Intestinal digestibilities of individual amino acids (AA), total AA and nitrogen (N) in three tropical protein-rich concentrates (sunflower cake, cotton seed meal and milkflow) and two legume forages (groundnut tops and cow pea tops) were estimated using the mobile bag technique with or without rumen pre-incubation for 16 h. For all feedstuffs the digestibilities of individual AA were close to total AA digestibility except for cystine and glycine which consistently showed the lowest digestibilities. However, the digestibilities of individual AA were different for different feeds. Rumen pre-incubation did not significantly influence the total AA digestibility within the examined feeds. Digestibility of total AA in the intact protein varied between 0.724 and 0.865 for legume forages and between 0.894 and 0.951 for concentrates. Using rumen pre-incubation the digestibilities of total AA varied between 0.749 and 0.826 for legume forages and between 0.897 and 0.956 for concentrates. There was no systematic deviation between total AA and N digestibilities. Sunflower cake showed the highest digestibilities of individual AA, total AA and N compared to other feeds while cow pea showed the lowest digestibilities of AA, notably cystine, lysine, methionine and proline. Milk flow had a low AA content (75.4 g AA/16 g N) implying use of low quality ingredients during feed formulation.