Comparison of the effects of slow-release urea vs conventional urea supplementation on some finishing cattle parameters: A meta-analysis

The aim of this study was to compare between the effects of slow-release urea (SRU) versus conventional urea (CU) supplementation on some finishing cattle parameters through the meta-analysis method using published scientific data. Data were extracted from nine experiments involving 532 bovines, 259 of which received CU and 273 who received SRU. When preparing the database, the applied sample unit was the average response for each article. Data from peer-reviewed articles published in indexed journals including the finishing phase of feedlot feeding were used. Furthermore, only studies applying conventional urea as a control group tested against slowrelease urea and reporting the mean and variability of dry matter intake (DMI), average daily gain (ADG), feed conversion (FC), hot carcass weight (HCW) and subcutaneous fat thickness (SFT) were included in the metaanalysis. The effect size for all parameters was calculated as mean difference (MD) or standardized mean difference (SMD) with a 95% confidence interval and heterogeneity determined by the Q test and I-2 statistics. A meta-analysis of random effects was conducted when I-2 > 50% and fixed effects with I-2 < 50% for each indicator separately with the means of control and experimental group. DMI (P = 0.6733), ADG (P = 0.1512) and FC (P = 0.1599) were similar between steers that received slow-release or conventional urea in feedlots. This similarity also extended to HCW (P = 0.1701) and SFT (P = 0.2709). The replacement of conventional urea with slow-release urea in the diet of steers finished in feedlot does not result in differences in performance and carcass traits.