The combined effects of feed-grade urea and urease inhibitor on growth performance, digestibility, blood biochemical indicator, and rumen environment of beef cattle

Yuan Zhou¹Xuerong Song²Dabo Fu²Lizbeth E Robles Jimenez³Manuel Gonzalez Ronquillo^4*Navid Ghavipanje⁵

• ¹Wuhan Academy of Agriculture Science, Wuhan city, China
• ²Wuhan Sunhy Biology Co. Ltd, Wuhan City, China
• ³Universidad Nacional Autonoma de Mexico, Instituto De Investigaciones En Ecosistemas Y Sustentabilidad, Morelia, Mexico
• ⁴Universidad Autónoma del Estado de México, Toluca, Mexico
• ⁵Faculty of Agriculture, University of Birjand, Bijand, South Khorasan, Iran

This study evaluated the combined effects of feed-grade urea (FGU) and urease inhibitor (HyUrit) as a partial replacement for vegetable protein source (soybean meal, SBM) in beef cattle diets on growth performance, digestibility, blood parameters, and rumen environment. Thirty Simmental bulls [average initial body weight (IBW) 445.67 ± 26.48 kg], were used in a completely randomized design (CRD) and fed feed-grade urea (FGU) with 0%, 5%, 10%, 15%, and 20% [dry matter (DM) basis] urease inhibitor (HU). There were no diet effects on IBW (p = 0.843), final body weight (FBW, p = 0.912), and average daily gain (ADG, p = 0.372). The intakes of DM (p = 0.906), OM (organic matter) (p = 0.939), CP (crude protein) (p = 0.898), NDF (neutral detergent fiber) (p = 0.565), and ADF (acid detergent fiber) (p = 0.616) were not affected between treatments. Feeding HU (at 10%, 15%, and 20%) led to higher digestibility of OM (p = 0.001), CP (p = 0.030), NDF (p = 0.001), and ADF (p = 0.001) compared to FGU group, however, digestibility of DM (p = 0.651) remained unaffected. Neither N intake (g/d, p = 0.898) nor N balance (g/d, p = 0.614) affect by FGU with different levels of urease inhibitor. Also, dietary treatment did not affect plasma concentration of Albumin (p = 0.080), and Insulin (p = 0.217) in beef cattle, however aspartate aminotransferase and alanine aminotransferase activity increased with the HU15 (15% HyUrit) (p = 0.002; 0.011 respectively), Total protein in plasma was lower for HU20 compared with Ctrl and HU5(5% HyUrit) (P=0.012). In vitro N-NH3 production at 0 (p = 0.0001), 0.5 (p = 0.0009), and 2 h (p = 0.0001) was higher in both FGU and HyUrit containing groups than Ctrl (SBM). Overall, the lower cost of FGU may justify its partial replacement of true protein meals in beef diets without impairing growth and health, in any case when there is an excess of FGU intake at a single dose rather than a TMR at a level of HU20 (20% HyUrit), decreasing the risk of alkalosis.