A Meta-Analysis of the Effects of Slow-Release Urea Supplementation on the Performance of Beef Cattle.

Abstract

Simple SummaryPlant-based feedstuffs, such as soybean meal and rapeseed meal are utilised to supply rumen degradable protein (RDP) and rumen undegradable protein (RUP) in the diets of ruminant animals (e.g., cattle, buffalo, sheep and goat). The RDP is utilised by rumen microbes for microbial protein synthesis. Microbial protein can contribute up to 80% of the protein requirement of ruminants. However, the use of plant protein sources in ruminant diets can be restricted based on their availability, costs and associated environmental impacts. Slow-release urea (SRU) is a non-protein nitrogen (NPN) source that allows for a partial replacement of vegetable RDP sources in ruminant diets by providing a sustained availability of ammonia for rumen microbial synthesis. Over the past three decades, extensive research has been conducted on the use of SRU in beef cattle diets. The current study analysed a combined dataset obtained from multiple research studies to derive quantitative and research-based evidence on the impact of a commercial SRU (Optigen®) on beef cattle performance. Results revealed that dietary supplementation of SRU improves the performance, profitability and environmental impacts of beef cattle production. Thus, this study demonstrates SRU as an effective NPN solution in beef cattle diets.Slow-release urea (SRU) is a coated non-protein nitrogen (NPN) source for ruminant nutrition. This study applied a meta-analytic technique to quantify the effect of a commercial SRU (Optigen®, Alltech Inc., Nicholasville, KY, USA) on the performance of beef cattle. Data were extracted from 17 experiments and analysed using the random-effects model to estimate the effect size of SRU on dry matter intake (DMI), crude protein intake (CPI), live weight gain (LWG) and feed efficiency (FE) of growing and finishing beef cattle. There was no effect of feeding SRU on the overall DMI and CPI of beef cattle. Dietary inclusion of SRU improved the overall LWG (+92 g/d/head) and FE (+12 g LWG/kg DMI/head) of beef cattle. Notably, SRU supplementation in growing cattle exhibited a better improvement on LWG (130 vs. 60 g/d/head) and FE (18 vs. 8 g LWG/kg DMI/head) compared with finishing cattle. Moreover, SRU showed consistent improvements on the LWG and FE of beef cattle under several study factors. Simulation analysis indicated that positive effects of SRU on LWG and FE improved profitability through reduction in feed cost and reduced the emission intensity of beef production. These results indicate that SRU is a sustainable NPN solution in beef cattle production.