Rumen fermentation, bacterial and total volatile fatty acid (TVFA) production rates in cattle fed on urea-molasses-mineral block licks supplement

Abstract

Of twenty rumen fistulated calves, four were allocated randomly to each of five tests. Animals were offered only wheat straw ad lib (T1), or in addition were supplemented with concentrate mixture (T2), or any one of three different types of UMMB-lick type A (T3), type B (T4) and type C (T5). A metabolism trial was conducted. Bacterial production rate (BPR) and total volatile fatty acid (VFA) production rate were estimated with an isotope dilution technique using 35S sodium sulfate and 14C sodium acetate, respectively.Nitrogen (N) balance in T1 animals were negative but, positive in other treatment groups. Total-N, ammonia-N, non-protein-N, TCA-precipitable-N in rumen on treatment groups T3 to T5 were comparable with T2 but higher than T1 (P < 0.01). Ammonia levels in rumen improved significantly on UMMB supplementation. Bacterial pool size and BPR were improved three-fold (P < 0.01) in T2 to T5 in comparison with T1. BPR per unit of digestible organic matter intake was higher on UMMB-lick type B and C than type A. Total VFA concentration, production rate and molar proportion of individual VFAs were higher (P < 0.01) and acetate to propionate ratio as well as non-glucogenic ratio were lower (P < 0.01) on treatment groups T3, T4 and T5 than on T1, while comparable with T2. YATP (gram of bacteria per mole of ATP) was 5.7, 8.9, 7.4, 9.7 and 9.6 in T1 to T5, respectively. Nitrogen incorporation efficiency by rumen bacteria was lower (P < 0.01) on supplementation of UMMB-licks compared to concentrate supplement. In conclusion, it would be possible for synergy in N and energy availability from UMMB-lick supplementation to wheat straw to stimulate microbial yield and fermentation in rumen like that from conventional concentrate supplement. The composition of UMMB-lick type B and type C was found to be better than type A in improving the microbial yield.