Context Beef cattle production in the tropics is based on the grazing system. Concentrate supplementation has a significant influence on carcass gain and meat quality. Additionally, the inclusion of some lipid feedstuffs, such as rumen-protected fat (RPF), can increase the net energy for weight gain, and be an alternative to increase the productive performance and carcass traits of grazing beef cattle. Aims This study evaluated the effects of RPF on performance, carcass traits and feeding behaviour of Nellore bulls in an intensive grazing system during the rainy season. Methods Twenty-four Nellore bulls (initial bodyweight of 454.0 ± 46.1 kg) were used in a randomised completed block design, based on initial bodyweight. The animals were distributed in 12 paddocks (two bulls per paddock) in a continuous grazing system and randomly assigned to one of two treatments: control (n = 6), a concentrate without added protected fat provided ad libitum, and RPF (n = 6), a concentrate with the addition of 3% protected fat (Nutricorp, Araras, São Paulo, Brazil) provided ad libitum. Statistical analysis was performed using the MIXED procedure of SAS 9.4 with paddock as the experimental unit (12 paddocks). The principal model included fixed effect of treatment and block as a random effect. For forage characteristics, the experimental period was a considered fixed effect. The study lasted 105 days, and was divided into four periods. At the end of each period, forage collections were performed, bulls were weighed and feeding behaviour was recorded. After 105 days, the bulls were slaughtered in a commercial slaughterhouse, and three 2.54-cm Longissimus dorsi steaks of each animal were collected to evaluate the colour, the chemical and physical composition, and the sensory analysis of the meat. Keys results The inclusion of RPF in the concentrate did not affect (P > 0.05) the final bodyweight, average daily gain, concentrate intake and feed efficiency, but there was a tendency (P < 0.07) for higher carcass weight for the bulls that received RPF. Bulls supplemented with RPF had a greater (P < 0.05) average carcass gain. For meat quality, an effect (P < 0.01) was observed for hue (25.32 and 27.91 for control and RPF, respectively). Conclusions The addition of 3% RPF in the concentrate ration has the potential to improve carcass traits and meat quality of beef cattle in an intensive pasture finishing system. Implications The inclusion of RPF will increase dietary energy density of grazing beef cattle with a tendency to increase carcass gain. This can be an opportunity to increase the production per animal and income of farmers.
