Performance, growth, and maturity of Nellore bulls

• Published in: Tropical animal health and production 2013-03, Vol.45 (3), p.795-803
• Main Authors: Costa e Silva, Luiz Fernando, de Campos Valadares Filho, Sebastião, Detmann, Edenio, Rotta, Polyana Pizzi, Zanetti, Diego, Villadiego, Faider Alberto Castaño, Pellizzoni, Samantha Gusmão, Pereira, Rafael Moura Guimarães
• Format: Article
• Language: English
• Subjects: Adipose tissue; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Biomedical and Life Sciences; Body Composition; Body weight; Brazil; Cattle - genetics; Cattle - growth & development; Cattle - physiology; Corn silage; Diet; Digestion; Dry matter; Energy Intake; Feedlots; Life Sciences; Male; Maturity; Nutrient requirements; Nutritional Requirements; Regular Articles; Veterinary Medicine/Veterinary Science; Weight Gain; Zoology
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-012-0291-1

The objectives of this study were to evaluate the dry matter intake (DMI), digestibility, average daily gain (ADG), microbial efficiency, empty body weight (EBW) gain, and body composition of Nellore bulls. Additionally, Nellore bull maturity was estimated, and the prediction equation for DMI, suggested by the Brazilian nutrient requirements system (BR CORTE; Azevêdo et al. 2010 ), was evaluated. Thirty-three Nellore bulls, with a mean initial weight of 259 ± 25 kg and age of 14 ± 1 months, were used in this study. Five animals were slaughtered at the beginning of the experiment (control group), and the remaining 28 were divided into 4 groups, each slaughtered at 42-day intervals. Their diet was composed of corn silage and concentrate (55:45). The power model was used to estimate muscle tissue, bone tissue, crude protein (CP), mineral matter (MM), and water present in the empty body, while the exponential model was used to estimate adipose tissue and ether extract (EE) present in the empty body. When expressed in kilograms per day, differences were observed ( P   0.05) digestibility, with the exception of EE digestibility. The equation suggested by BR CORTE correctly estimates the DMI of Nellore bulls. ADG was not affected ( P  > 0.05) by time spent in the feedlot. No differences were observed ( P  > 0.05) for microbial efficiency; a mean value of 142 g microbial crude protein/kg total digestible nutrients was achieved. The muscle and bone tissues, CP, MM, and water present in the empty body increased as the animal grew, although at a lower rate. The adipose tissue and EE present in the empty body increased their deposition rate when the animal reached its mature weight. Maturity is defined as when an animal reaches 22 % EE in the empty body, which corresponds to 456 kg of EBW in Nellore bulls. Therefore, this study can conclude that the feedlot time period does not affect DMI, nutrient intake, ADG, or microbial efficiency. The equation proposed by BR CORTE (Azevêdo et al. 2010 ) correctly estimates the DMI of Nellore bulls, which reach maturity when an EBW of 456 kg is attained.