Effect of combinations of feed-grade urea and slow-release urea in a finishing beef diet on fermentation in an artificial rumen system

Abstract

This study evaluated the effect of combinations of feed-grade urea and slow-release urea (SRU) on fermentation and microbial protein synthesis within two artificial rumens (Rusitec) fed a finishing concentrate diet. The experiment was a completely randomized, dose–response design with SRU substituted at levels of 0% (control), 0.5%, 1%, or 1.75% of dry matter (DM) in place of feed-grade urea, with four replicate fermenters per dosage. The diet consisted of 90% concentrate and 10% forage (DM basis). The experiment was conducted over 15 d, with 8 d of adaptation and 7 d of sampling. Dry matter and organic matter disappearances were determined after 48 h of incubation from day 9 to 12, and daily ammonia (NH3) and volatile fatty acid (VFA) production were measured from day 9 to 12. Microbial protein synthesis was determined on days 13–15. Increasing the level of SRU quadratically affected total VFA (Q, P = 0.031) and ammonia (Q, P = 0.034), with a linear increment in acetate (L, P = 0.01) and isovalerate (L, P = 0.05) and reduction in butyrate (L, P = 0.05). Disappearance of neutral detergent fiber (NDF) and acid detergent fiber (ADF) was quadratically affected by levels of SRU, plateauing at 1% SRU. Inclusion of 1% SRU resulted in the highest amount of microbial nitrogen associated with feed particles (Q, P = 0.037). Responses in the efficiency of microbial protein synthesis fluctuated (L, P = 0.002; Q, P = 0.001) and were the highest for 1% SRU. In general, the result of this study showed that 1% SRU in combination with 0.6% urea increased NDF and ADF digestibility and total volatile fatty acid (TVFA) production.

Effect of Commercial Slow-Release Urea Product on in Vitro Rumen Fermentation and Ruminal Microbial Community Using RUSITEC Technique

“…The absent effect of increasing the dose of SRU in the diets from 0, 0.28 to 0.56% on nutrient digestibility is in agreement with some studies [7,28,29], but it is consistent with other studies [9,30]. With using continuous culture system, Xin et al [7] found no differences in the nutrient digestibility of corn-based dairy cow diet supplemented with either feed grade urea or polyurethane coated urea.…”

“…Gardinal et al [29] reported that the nutrient digestibility in the total digestive tract was not affected by adding 2% polymercoated SRU in the diet of Nellore steers. In contrast, Alipour et al [9] reported quadratically increased the digestibility of NDF and ADF of a high concentrate diet with increasing SRU dosages from 0, 0.5, 1.0 to 1.75% in high concentrate diet in Rusitec. Another study has been demonstrated to increase total tract DM and CP digestibility when fed polymer-coated SRU to lactating dairy cows [6].…”

“…Supplementation of SRU also affected rumen microbial diversity and community composition. Alipour et al [9] suggested an improvement of brolytic bacterial activity by adding SRU in a high-grain diet. Ferme et al [10] reported an inhibition of major ammonia producing bacteria (e.g., Prevotella ruminantium and Prevotella bryantii) and thus a reduction in NH 3 -N concentration in continuous culture.…”

“…Ferme et al [10] reported an inhibition of major ammonia producing bacteria (e.g., Prevotella ruminantium and Prevotella bryantii) and thus a reduction in NH 3 -N concentration in continuous culture. Moreover, several studies reported that the lower dose of SRU actually resulted in better growth performance of yak fed diet supplemented with 1% than with 2% of SRU [8] or the higher bre digestibility of a high-grain diet with 0.5 and 1% SRU than 1.75% SRU supplementation in Rusitec [9]. Whereas, Tedeschi et al [5] found no improvement in growth performance when urea was substituted by a SRU at levels normally found in feedlot cattle diets.…”

Effect of Slow-Release Urea Administration on Production Performance, Health Status, Diet Digestibility, and Environmental Sustainability in Lactating Dairy Cows

“…Notably, there is limited published information on the effect of feeding urea on real enteric CH 4 production. Alipour et al (2020) [42], and Rebelo et al (2019) [43] showed that feeding two sources of coated and non-coated urea did not affect enteric CH 4 yield measured in an in vitro ruminal fermentation system or beef cattle, respectively. However, Libera et al (2021) showed that the CH 4 production at the ruminal level reduced after using urea combined with enzymes and cereals in dairy cows.…”