Performance, body composition and net requirements of protein and energy for weight gain in steers supplemented with or without addition of lipids / Desempenho, composição corporal e exigências líquidas de proteína e energia para ganho de peso em novilhos suplementados com ou sem adição de lipídios

This research aimed to evaluate the performance, body composition and net requirements for protein and energy in grazing Nellore steers supplemented with or without addition of lipids. Twenty-eight steers, 301 ± 5.8 kg BW, were used in the experiment. The comparative slaughter method was used, with four steers used as references. The remaining 24 steers were randomly distributed into four groups, during 180 days, according to treatment: only Panicum maximum cv. Mombasa grass; Mombasa grass with concentrated supplementation based on soybean meal; Mombasa grass with concentrate containing lipids from soybean oil; and Mombasa grass with concentrate containing lipids derived from soybean grains. The total DMI of the steers fed only the pasture did not differ (P > 0.05) from the average intake of the treatments with or without addition of lipids. There were no differences (P > 0.05) between treatments for total daily gain, carcass and non carcass for protein, energy and fat. The requirements of protein and energy did not differ (P > 0.05) among the treatments. When the pasture is of good quality, supplementation does not alter the body composition or the net requirements of protein and energy for weight gain. The supplementations with higher concentrations of lipids (oil and grain) were not enough to promote greater gains in fat and energy in carcass.

Esta pesquisa teve como objetivo avaliar o desempenho, composição corporal e requisitos líquidos para proteínas e energia de novilhos Nelore em pastejo suplementados com ou sem adição de lipídios.Foram utilizadas no experimento vinte e oito novilhos, 301 ± 5,8 kg PC. O método comparativo de abate foi utilizado, com quatro novilhos utilizados como referências. Os 24 restantes novilhos foram distribuídos aleatoriamente em quatro grupos, durante 180 dias, de acordo com o tratamento: apenas Panicum maximum cv. Grama Mombasa; Grama de Mombasa com suplementação concentrada à base de farelo de soja; Grama de Mombasa com concentrado contendo lipídios de óleo de soja; e Mombasa com concentrado contendo lipídiosderivados de grãos de soja. O CMS total dos novilhos alimentados apenas com a pastagem não diferiu (P>0,05) da ingestão média dos tratamentos com ou sem adição de lipídios. Não houve diferenças (P> 0,05) entre os tratamentos para o ganho diário total, carcaça e não carcaça para proteínas, energia e gordura. Os requisitos de proteína e energia não diferiram (P> 0,05) entre os tratamentos.Quando a pastagem é de boa qualidade, a suplementação não altera a composição corporal ou os requisitos líquidos de proteína e energia para ganho de peso. As suplementações com maiores concentrações de lipídios (óleo e grão) não foram suficientes parapromover maiores ganhos de gordura e energia na carcaça.

Performance, nitrogen balance and microbial efficiency of beef cattle under concentrate supplementation strategies in intensive management of a tropical pasture.

The objective of this study was to evaluate the effect of concentrate supplementation strategies on the nutritional characteristics of beef cattle in intensive management of tropical pasture. Twenty-four Nellore steer at 250 kg body weight (BW) were used, divided into two plots, with 12 animals in each plot. The experimental area consisted of 32 paddocks with 0.25 ha of Panicum maximum cv. Mombaça. The experiment consisted of 96-day experimental periods, with three periods of 32 days. The strategies studied were P = exclusively on pasture and without concentrate supplementation (control), ES = pasture and supplemented with a concentrate low in protein, PS = pasture and supplemented with high protein content, and PES = pasture and supplementation with balanced protein-energy. There was reduced intake of DM in animals of the treatment P in relation to supplemented pasture, regardless of supplementation. Animals fed on ES showed an intake of more nutrients than the animals on PS. The CP and TDN were also lower in P than in pastures where animals received the additional types of concentrate, and the PS animals showed greater digestibility of CP and TDN than the ES animals. However, the animals exhibited similar weight gains. Animals on P ingested smaller amounts of N and had lower fecal excretion compared to the supplemented animals, but there was no difference between treatments in nitrogen balance. Urea nitrogen and urea from the blood were higher in the supplemented animals than in animals fed on pasture; these levels were also higher in PS animals compared to animals receiving ES. Both the purines absorbed and microbial protein production were similar between treatments. However, the animals fed with concentrate supplementation, independent of the strategy involved, showed higher microbial efficiency compared to animals fed exclusively on pasture.