PSIV-B-24 Late-Breaking: Effect of initial body weight variation on growth performance of finishing Nellore cattle
Abstract The increased number of beef cattle entering feedlot operations in Brazil has increased, thus leading to increased productivity, livestock density rate, and improved carcass traits. The age and condition in which animals enter the feedlot is often neglected and may result in increased pen heterogeneity and might impact the growth development of the animals. The objective of this study was to evaluate the effect of the initial weight variation indicator (IWVI) on confined Nellore breeds on productive performance. A total of 382 pens (38,850 animals) were evaluated for 90 days. The variables evaluated were (IWVI), average daily gain (ADG), gain efficiency (G:F) and net feed conversion (nFC). The experimental design was determined by the amplitude of the mean and high volume of homogeneity. A non-parametric analysis was performed using the Kruskal-Wallis test for the comparison of groups, and there was a significant difference using the Mann-Whitney test for the comparison of experimental groups 2 to 2. Significance was determined at (P < 0.017). The highest ADG was 1.59 kg, observed for the pens with lower IWVI. The lowest ADG was 1.46 kg, observed in the pens with higher IWVI. The lower IWVI showed higher G:F (6.36) and nFC (131.01 kg) compared to more variable initial weight pens (1.82 and 148.09 kg, respectively). Lower initial weight variations per pen had a positive effect on average daily gain, gain efficiency and net feed conversion. Initial body weight variation seems to be an important factor feedlots should consider upon Nellore cattle arrival.