Protein solubility in rice straw + legume rations containing varying levels of flemingia in the rumen of cattle

The authors determined in sacco at the effects of varying tannin levels from flemingia on the solubility of protein in various rice straw (RS) + legume diets. Rations containing rice straw (50 and 70%) in combinations with five low tannin-containing and highly digestible legume species (Stylosanthes guianensis CIAT 184, Desmanthus virgatus, Leucaena leucocephala, Desmodium ransonii, Gliricidia sepium) and a tannin-rich legume (Flemingia macrophylla) at 0, 10, and 20% enclusion levels were used. In sacco CP and DM disappearance and ruminal degradation characteristics of the test rations were determined by using nylon bags where approximately 3-9 samples (replicated three times) were incubated (4, 8, 16, 24, 48, and 72 hours) in the rumen of a fistulated cattle. The solubility of CP and DM of the rations was calculated by fitting the amount of CP and DM degraded per incubation Period to the equation: D = a+b (1-e sup ct). Findings showed that the rations' CP content ranged from 10.45 to 14.00%, with rensonii ration having the highest CP content and the stylo ration, the lowest. Rations without flemingia had significantly the highest CP content (12.83%), followed by those with 10% flemingia inclusion (12.48%) and then by those with 20% flemingia (12.05%). The inclusion of 70% RS effectively reduced the rations' CP content from 13.88 to 11.03%. The inclusion of either 10 or 20% flemingia in the ration effectively increased the rations' cell wall contents from 60-61% (without flemingia) to 62.47% (with flemingia). The amount of degraded DM was significantly highest with gliricidia ration at all incubation periods. The rations with 20% flemingia had significantly the lowest DM degradation. Consistent at all incubation periods, the ration with ransonii showed significantly high amounts of protein disappearing from the nylon bags. The rations without flemingia had significantly the highest amounts (45.85-71.13%) of protein diappearing from the nylon bags at all incubation periods among those with 10% flemingia (44.32-67.39%) and 20% flemingia (43.46-65.21%). The significantly lower values for the rations with 10 and 20% flemingia show that some of the dietary proteins may have been rendered insoluble. There were significant differences in soluble fraction, rate constant, and effective degradation (ED) of DM and CP for all the test rations. The ED of DM ranged from 49.60 to 60.58%, with gliricidia ration having the highest ED, while that of CP ranged from 50.58 to 59.57% with rensonii ration having the highest ED. The enclusion of flemingia in the rations, regardless of levels, significantly reduced the water insoluble CP fraction of the rations. The effect of flemingia in protecting the dietary protein of the basal ration was clearly shown in the lowering of CP's ED from 57.47% (without flemingia) to 53.60% (with 10% flemingia) to 52.66% (with 20% flemingia)