Slaughter weights for the production of young bull cattle. 1. Performance on feedlot and cost of production

To obtain the adequate slaughter weights and costs of production of young bulls, a feedlot study was conducted at Embrapa Pecuaria Sudeste, with 234 crossbred Blonde d'Aquitaine x Nellore (BN); Canchim x Nellore (CN); Limousin x Nellore (LN); Piedmontese x Nellore (PN); and straightbred Canchim (CA) and Nellore (NE) in 1994,1995 and 1997. At the beggining of the experiment, the animals had 12 months of age and the BN, CA, CN, LN weighed 265 kg, the NE 214 kg and the PN 237 kg. The slaughter weights (TRAT) of 400 (1); 440 (11) and 480 kg (111), except for NE bulls (380, 410 and 440 kg), were tested. A diet with 13% crude protein and 70% total digestible nutrients, based on 50% whole plant corn silage and 50% concentrate, on a dry matter basis, was fed ad libitum. The measurement of weights of the animals were performed after fasting for 16 hours. Data were submitted to the analysis of variance and the means compared by SNK tests. The estimated means of daily weight gain (DWG), daily dry matter intake (DMI), kg and as a percentage of live weight, the feed:gain ratio (FG) and days on feed for TRAT I; II and III were 1.56; 1.49 and 1.44 +/- 0.03 kg; 9.01; 9.01 and 9.21 +/- 0.13 kg; 2.58; 2.44 and 2.45 +/- 0.04%; 5.92; 6.26 and 6.49 +/- 0.12; 71.3; 95.6 and 115.3 +/- 2.1 days, respectively. The effects of year, genetic group and TRAT were significant for DWG, DMI and FG. The interactions between genetic group and TRAT were not significant. There was an increase in the cost of production of 15 kg of carcass in the feedlot from 39.14 to 40.31 or 40.49 reais with the increase in the slaughter weight from 400 to 440 or 480 kg live weigth, respectively. The monthly net income of the capital invested was reduced from 1.0% to 0.7% or 0.6% for TRAT I, II or III, respectively.