Effect of the dietary level of cull pinto beans (Phaseolus vulgaris) on ruminal fermentation, kinetics, and digestibility of hair lambs

Abstract

-The objective was to evaluate the effect of three levels of cull pinto beans (CPB; Phaseolus vulgaris) on ruminal fermentation, kinetics, and nutrient digestibility in hair lambs. Six cannulated lambs averaging 56.6±3.8 kg were used and were randomly assigned to one of three treatments. Treatments were: 0.0 kg kg -1 of CPB in the supplement (control); 0.25 kg kg -1 of CPB in the supplement (CB25); and 0.40 kg kg -1 of CPB in the supplement (CB40). Dry matter intake, ruminal pH, NH 3 , and volatile fatty acid (VFA) concentration, methane production, Kp (passage rate), MRT (mean retention time), and digestibility of dry matter, crude protein, and neutral detergent fiber were evaluated. Data were analyzed in a Latin square design, repeated in line, by MIXED procedure of SAS. Estimates used for Kp and MRT were obtained by a non-linear regression model (PROC NLIN). Dry matter intake was reduced by supplementation of CPB. No differences were found in ruminal pH or ruminal NH 3 . During the trial, differences were found for ruminal VFA concentration (mM), which were greater for the CB25 group. The propionate:acetate ratio was greater for the CB40 treatment. Methane production (mM/m) differed among treatments, but it was the greatest for the CB40 group. Passage rate (kg kg -1 /h) and MRT (h) were similar among treatments and the digestibility (kg kg -1 ) of dry matter, crude protein, and neutral detergent fiber was not different among treatments. The inclusion of 0.25 kg kg -1 of CPB in the diet of hair lambs allows for appropriate nutrient digestion without affecting Kp and MRT and increases the molar proportion of the ability of VFA to maintain acetate:propionate ratio without increasing methane production.