Discipline: Animal Science
The effects of varying tannin levels from Fleminiga macrophylla on the solubility of protein in rice straw legume diets in the rumen of cattle were determined. Rations containing rice straw (50 and 70%) in combinations with five low tannin-containing and highly digestible fodder legume species (Stylosanthes guianensis CIAT 184, Desmanthus virgatus, Leucaena leucocephala, Desmodium rensonii, Gliricidia sepium) and a tannin-rich legume species (Flemingia macrophylla) at 0,10 and 20% inclusion levels were used following a 2 x 5 x 3 factorial arrangement in CRD. In sacco protein and dry matter (OM) disappearance and ruminal degradation characteristics of the test rations were determined. Samples were incubated in the rumen for 4, 8, 16, 24, 48 and 72 hr. The solubility of protein and OM of the rations was calculated by fitting the amount of protein and OM degraded per incubation period to the equation D = a+b (1 - ect). The soluble fractions, rate constant and effective degradation (ED) rate were computed. The rations without Flemingia had the highest crude protein (CP) content. The inclusion of Flemingia significantly increased the rations' neutral detergent fiber (NOF) and lignin contents but effectively reduced the CP contents, CP degradation, OM degradation, soluble fraction and ED values. The significantly lower soluble fraction and ED values of the rations with 10 and 20% Flemingia show that some of the dietary proteins may have been rendered insoluble in the rumen and may be effectively utilized as source of by-pass proteins.