Effect of Post-Ruminal Urea Supply on Growth Performance of Grazing Nellore Young Bulls at Dry Season

Abstract

The objective of this study was to evaluate the effect of the use of post-ruminal urea on performance, nitrogen metabolism and the ruminal environment of Nellore cattle reared on pasture during the dry season. In experiment 1 (Exp. 1), nine ruminal-cannulated Nellore steers, 30 ± 2 months old (651 ± 45 kg body weight (BW)), were allotted to a 3 × 3 Latin triple square. In experiment 2 (Exp. 2), 84 Nellore bulls, 18 ± 3 months old (315 ± 84 kg BW), were distributed in complete randomized blocks, by initial BW. Protein supplements were supplied daily, in the amount of 2 g/kg BW, and consisted of either CONT: protein + conventional urea (50% CP), PRU: protein + post ruminal urea (50% CP) and U + PRU: protein + urea conventional + post-ruminal urea (70% CP). The paddocks were composed of Urochloa brizantha cv. Marandu grass. In Exp. 1, there was no treatment effect for DM, OM, NDF, forage intake, and CP, but there was a higher intake for PRU (p < 0.005) and a higher digestibility for U+ PRU (p = 0.001). There was no effect on ruminal pH or NH3-N concentration (p ≥ 0.232), but there was an interaction between treatment and time for them (p < 0.039). Furthermore, there was a treatment effect on the total SCFA concentration, with CONT being higher than the others. A difference in the acetate:propionate ratio was found (p < 0.027), with a greater relationship for PRU and U + PRU. A treatment effect (p = 0.049) was found for the propionate proportion, with a higher proportion in the CONT. Nitrogen intake was consequently lower for the CONT and higher urinary excretion for the U + PRU (p = 0.002). Animals supplemented with CONT showed a tendency to have more Bacteria and fewer Archaea (p = 0.086). In Exp. 2, there was a treatment effect for the disappearance rate of the supplement (p < 0.001). Intake was faster for PRU and CONT, but performance was not affected by PRU (p = 0.311). The use of post-ruminal urea alters the microbial population, but does not affect performance. Therefore, supplementation with post-ruminal urea presented similar results compared to conventional urea. Ruminal and blood parameters and animal performance were not influenced by treatments.

Endophytes in Agriculture: Potential to Improve Yields and Tolerances of Agricultural Crops

“…N fertilizers, such as urea, are common practice to improve crop yields, as they are the most effective crop health improvers. However, urea can be harmful to the environment and livestock if inappropriately treated [ 212 ]. Using alternate sources to improve N bioavailability, such as EAP, greatly reduces the threat to the environment and the effort required to sustain healthy crops [ 213 , 214 ].…”

Conventional Feed-Grade or Slow-Release Coated Urea as Sources of Dietary Nitrogen for Fattening Lambs

“…In our research, the urea content per kg is equivalent to 27 g of CP content (approximately 26% of the RDP) in both experimental diets, and this rather low proportion could limit the effect of the type of urea, especially in high-protein diets. Nevertheless, the lack of an effect of replacing conventional urea with SRU on the ruminal ammonia concentration has also been reported in vitro and in vivo when feeding diets with a lower CP content (8 to 15% on DM basis), where urea represented more than 25% of the total dietary CP [9,17,[43][44][45]. The concentration of ammonia in the rumen is the result of the balance between the degradation and absorption of dietary or endogenous sources of N, and the synthesis of microbial protein.…”