Effect of Different Slow-Release Urea on the Production Performance, Rumen Fermentation, and Blood Parameter of Angus Heifer.

Simple Summary: Slow-release urea can slow down the degradation rate of urea in the rumen, improving nitrogen utilization efficiency and promoting the growth of rumen microorganisms. However, different slow-release urea may have variance functions. This study used two kinds slow-release urea, polymer-coated urea and gelatinized starch urea, to evaluate the effects on Angus heifers. We found that polymer-coated urea was able to improve the feed efficiency of cattle, and it also increased the daily gain. In rumen, adding polymer-coated urea increased the content of volatile fatty acids like acetate and propionate. In addition, polymer-coated urea increased the relative abundance of some friendly bacteria in the rumen, like Paraprevotella. Thus, we believe that polymer-coated urea can improve the production performance of Angus heifers and bring about more economic benefits. This study investigated the effect of replacing part of the dietary soybean meal with either polymer-coated urea or gelatinized starch urea on the production performance, blood indexes, and ruminal fermentation of Angus heifers. A total of 210 purebred Angus cattle (BW = 314.26 kg) were divided into three groups: the no urea group (CON), the polymer-coated urea group (PCU), and the gelatinized starch urea group (GSU); 20 g/kg polymer-coated urea or 25 g/kg gelatinized starch urea was used to replace part of soybean meal in the concentrate feed, according to the principle of isometabolic energy and isonitrogenous. The result showed that the PCU group had higher ADG and ADF apparent digestibility, while it had a lower feed–weight ratio. On the 86th day, the serum albumin (ALB) content in the PCU group was significantly higher than that in the CON group. In rumen, compared with the CON group, the contents of acetic acid and total volatile fatty acid were significantly higher in the PCU group, whereas butyric acid and propionic acid were significantly higher in the PCU group and GSU group. Ruminal bacterial diversity analysis found that the abundance of Firmicutes was higher in the PCU group at the phylum level, and an inverse result was observed in Bacteroidetes. The abundance of Paraprevotella was higher in the PCU group, whereas higher abundance of Prevotella was found in the GSU group at the genus level. These results indicate that slow-release urea can replace part of soybean meal in the diet, and the amount of substitution in this trial had no diverse effect on the performance of Angus heifers. [ABSTRACT FROM AUTHOR]