Effects of urea supplementation on rumen fermentation characteristics and protozoa population<i>in vitro</i>

Abstract

Cotton straw is used as a roughage source in conjunction with maize in draught prone regions in the world for animal production. However, this diet generally contains relatively low rumen degradable protein compared with its supply of fermentable metabolizable energy; therefore leading to a suboptimal animal performance and high methane production. Although urea supplementation is known to improve microbial crude protein (MCP) production and animal production, the recommended levels of urea supplementation range between 1% and 6.7% according to literatures. This in vitro study was conducted as a preliminary investigation to determine the impact of urea supplementation up to 3% (as dry matter in the diet) on rumen fermentation characteristics and protozoa population, on typical maize meal and cotton straw-based diet used for sheep production in XinJiang province, China. MCP production was improved by 64% when urea increased from 0% to 2% in the diet, with no additional benefit observed at 3% urea in the diet. On the other hand, methane production was reduced when urea increased from 0% to 3% in the diet. These results indicated that 2% urea supplemented under the current feeding condition may improve MCP production and reduce methane production. However, further in vivo study is needed to confirm that 2% urea in the diet would not cause adverse effects on animal health.