Abstract
Four experiments were conducted to examine the effect of different levels of nitrogen (RDP) from urea, mustard oil cake and legume fodder (Lathyrus sativus) on digestibility of nutrients, rumen fermentation characteristics, microbial nitrogen (MN) supply, the contribution of RDN to MN and nitrogen (N) status of indigenous cattle. Experiment 1, 2 and 3 examined above mentioned objectives in indigenous cattle fed different levels of N (RDP) from three different sources i.e. urea, mustard oil cake and legume fodder (Lathyrus sativus) in straw-based iso- caloric diet and experiment 4 was designed to investigate the effect of different levels of energy with high RDP diet on the above parameters.
In Expt. 1, 2 and 3, four ruminally cannulated indigenous cattle (Bos indicus) of about 179 kg live weight (4-5 years of age) were given four iso-caloric (7.0 MJ/kg DM) straw-based diets containing 4.1, 6.3, 8.3 and 12.4 g RDP/MJ ME (0.5, 0.25, 1.0 and 1.5 times ARC, 1984 maintenance requirement) in a 4 X 4 Latin Square Design for each period of 28 days. The incremental level of RDP over control (4.1 g/MJ ME) is either from urea (Expt. 1) or mustard oil cake (Expt. 2) or legume fodder (Expt. 3) source. Feed intake was restricted to 2% live weight.
Increasing level of RDP intake either from urea or mustard oil cake or legume fodder linearly increased the digestibility of all nutrients, the concentration of ammonia-N, Total-N, TCA ppt-N, NPN and TVFA in the rumen liquor. The daily MN supply estimated from the excretion of urinary purine derivatives, increased linearly with increasing level of RDP in the diet. However, efficiency of MN supply (EMNS) increased linearly only in the case of legume fodder and the EMNS (g MN/kg DOMR) was the highest (25.70 in Expt. 1, 24.73 in Expt. 2 and 26.97 in Expt. 3) for the diet containing 8.3 g RDP/MJ ME and showed curvilinear response with higher RDP level (12.45 g/MJ ME). The efficiency of contribution of RDN to MN was linearly decreased with the increasing levels of RDP intake for all three experiments. The N balance also increased linearly in response to increasing level of RDP intake either from urea or mustard oil cake or legume fodder. Pooled data from all the three experiments showed that the supplemental RDP from legume gave better performance in respect of EMNS and N status of indigenous cattle.