INTRODUCTION

1. Phenotypic correlations between residual feed intake, growth, carcass traits and reactivity in Nellore bulls (Bos indicus). Tiago Roberto Stella †, Paulo Roberto Leme †, Saulo da Luz e Silva †, José Bento Sterman Ferras †, Rodrigo da Costa Gomes †, José Carlos Machado Nogueira Filho †, Pedro Zillig da Silva Neto † †Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo, Pirassununga, SP, Brazil§Corresponding author: tiagostella@usp.br RESULTS INTRODUCTION Residual feed intake (RFI) is a feed efficiency trait phenotypically independent of growth rate and mature weight. Breeding beef cattle for improved RFI may reduce feeding costs and increase profitability of beef business. However, associations between RFI with production traits and animal behaviour were not studied in Nellore cattle Table 1 – Means and standard error of means of age,weaning weight,birth weight, yearling weight, post weaning weight gain, reactivity score, feed intake, RFI, feed convertion, Longissimus muscle area and backfat thickness. OBJECTIVE In this sense, it was aimed to evaluate phenotypic correlations between residual feed intake (RFI), growth, carcass traits end animal behavior in Nellore bulls. • MATHERIAL AND METHODS • A total of 96 Nellore young bulls, born in 2005 and 2006. • The weaning weight (WW), birth weight (BW), yearling weight (YW), post weaning weight gain (WG) and reactivity score (animal agitation when restrained in the squeeze chute) were take. • The animals were evaluated for RFI in 2007 and 2008, respectively. • They were fed individually for 68 days with a diet containing 68% of TDN and 14.3% CP.. • The weight and ultrasonic measurements of Longissimus muscle area (REA) and backfat thickness (BF) on the 12th and 13th ribs were obtained every 21 days. • Pearson correlation analysis was performed • Probabilities lower than 5% were considered statistically significant. Table 2 -Phenotypic correlations between residual feed intake, rate of gain of carcass components and production rates of Nelore bulls WW= weaning weigth, BW= birth weight, YW= yearling weight, WG= post wearning weight gain, FCR= feed convertion, RFI= residual feed intake, REA= Longissimus muscle area, BF= backfat thickness, RCT= reativity *** = P<(0,001), ** = P<(0,05), * = P< (0,1). CONCLUSION Residual feed intake was not associated with growth, body weight and carcass traits in Nellore