Características de desempenho e eficiência alimentar de touros Purunã em crescimento de três classes de consumo alimentar residual

This trial aimed to evaluate the performance, feed intake and feed efficiency traits of Puruna growing bulls of three groups of residual feed intake (RFI): efficient, intermediary and inefficient. There were used 110 growing bulls with average of 10 months of age and 233kg of body weight (BW) which were randomly allocated in individual feedlot pens. The diet was composed, in dry matter (DM) basis, by 420g/kg of concentrate and 580g/kg of corn silage, and was offered ad libitum. Daily dry matter intake (DMI) and average daily gain (ADG) were assessed during 112 days. Initial and final BW and ADG not differed between the efficiency groups and showed mean values of 233kg, 360kg and 1.14kg/d. Mean values of 7.19, 7.62 and 8.10kg/d to DMI and -0.48, -0.01 and 0.48kg DM/d to RFI were observed in efficient, intermediary and inefficient groups. Feed conversion ratio (FCR) and gross feed efficiency (GFE) not differed between efficient and intermediary groups, which showed means of 6.65kg DM/kg gain and 153g gain/kg DM. Inefficient group showed higher FCR and lower GFE, with mean values of 7.40kg DM/kg gain and 138g gain/kg DM. Partial efficiency of growth (PEG) differed between the efficiency groups and showed means of 294, 277 and 255g gain/kg DM for growth in efficient, intermediary and inefficient groups. RFI showed moderate to high correlations with FCR, GFE and PEG, and decrease of RFI resulted in decrease of FCR in 12.2%, increase of GFE in 13.3% and increase of PEG in 15.5%. Efficient Puruna growing bulls (low RFI) present lower feed intake, but maintains the same production level that inefficient ones (high RFI). Thus, RFI classification allows identifying animals with potential to improve the productive efficiency of herd.