The objective of this study was to evaluate performance and nutritional traits of beef cattle raised on pastures, castrated at different ages, with and without supplementation. Forty-four crossbred young bulls with predominance of Zebu breed at initial average age of 120±30 days were used in the experiment. Animals were distributed in a completely randomized design in a factorial arrangement with four ages of castration and two supplementation systems. The animals were distributed into four groups and placed on Brachiaria decumbens Stapf pastures, where they were fed concentrate supplementation or mineral salt ad libtum (control). Animals were castrated at 120, 240 and 360 days of age with average body weight of 115, 175 and 276 kg, castrated or not, in each supplementation group. Concentrate supplement composition and the amount supplied to the animals varied according to the time of the year and development phase of the animals. Trials were carried out to evaluate nutritional variables in each of the following phases: suckling, growth in the dry season and growth in the dry/rainy transition season. Concentrate supplementation improved the use of pasture, although it may have caused substitutive effect in all seasons evaluated. Castration of the animals before the dry season impaired animal development until the following dry/rainy transition season, especially when carried out during weaning. Concentrate supply may reduce some effects of this stress.

The objective of this experiment was to estimate the requirements of energy, protein and macrominerals of grazing crossbreds calves, in Brachiaria decumbens Stapf pasture, castrated at different ages, with and without supplementation. Forty-seven young calves at initial age of 120±30.1 days and 115.3±1.97 kg of live weight were used. To estimate net energy requirements for weight gain, a regression equation between energy retained in the gain and empty body weight gain and metabolic empty body weight was obtained. For estimation of net protein requirements for weight gain, a regression equation was adjusted between protein retained in gain and empty body weight gain and energy content of this gain. Net requirements of Ca, P, Mg and Na for weight gain were determined by the equation Y' = a.b. Xb-1, in which a and b represent the intercept and the coefficient of the alometric equation of macromineral body content prediction, respectively. Neither castration nor concentrate supplementation affects body weight gain net requirements, except the ones of Ca, which were higher for non-castrated animals.

O objetivo neste estudo foi avaliar as condições nutricionais de tourinhos em aleitamento, a pasto, recebendo suplementação com concentrados proteicos durante a época de transição águas-seca. Foram utilizados 52 bezerros mestiços com idade média inicial de 130 dias. Os animais foram distribuídos em quatro lotes, alojados em piquetes de Brachiaria decumbens Stapf junto com suas mães, onde receberam uma das quatro estratégias de suplementação: três suplementos concentrados, ou sal mineral (controle). Os suplementos concentrados diferiram quanto ao nível de proteína. Após 45 dias, realizou-se a avaliação nutricional dos animais, que incluiu a estimação do consumo e da digestão de nutrientes e das características do metabolismo proteico. A estimação do consumo e da digestibilidade foi feita utilizando-se os indicadores: LIPE®, dióxido de titânio e fibra em detergente neutro indigestível. Realizou-se ainda coleta de amostras de urina e de sangue. O efeito de suplementação e os efeitos linear e quadrático do nível de proteína no concentrado foram avaliados pela decomposição da soma de quadrados em contrastes ortogonais, adotando-se α = 0,10. O consumo de concentrado substituiu parte do pasto ingerido pelos bezerros e aumentou a ingestão de proteína, a digestibilidade da matéria seca e matéria orgânica, o teor de nutrientes digestíveis totais e a excreção de nitrogênio na urina. O nível de proteína no suplemento tem efeito linear positivo sobre a ingestão diária de proteína, a digestibilidade de todos os nutrientes e o teor de nutrientes digestíveis totais e efeito quadrático sobre a excreção de nitrogênio na forma de ureia na urina.

The objective of this study was to evaluate the nutritional status of grazing nursing young bulls supplemented with concentrates with different protein levels during the rainy-dry season transition. Fifty two crossbred Nellore calves with initial mean age of 130 days were divided into four lots, housed in paddocks of Brachiaria decumbens Stapf and received one of the four different supplementation strategies: three different concentrate supplements, or mineral salt (control). The levels of protein in the concentrate supplements varied. After 45 days, the nutritional evaluation of animals, which included the prediction of intake and digestion of nutrients and characteristics of protein metabolism, was made. The prediction of intake and digestibility used the indicators LIPE®, titanium dioxide and neutral detergent fiber indigestible. Urine and blood samples were collected too. The supplementation effect, and the linear and quadratic effects of the level of protein in the concentrate were evaluated by the decomposition of the sum of squares into orthogonal contrasts, adopting α = 0.10. The concentrate intake replaced part of the pasture ingested by the calves and increased protein intake, the digestibility of dry and organic matter, the total digestible nutrients content, and the nitrogen excretion in urine. The level of protein in the supplement has a positive linear effect on the daily protein intake, the digestibility of all nutrients and the total digestible nutrients content, and quadratic effect on the excretion of nitrogen as urea in the urine.

Foram avaliados os efeitos de épocas alternativas de nascimento sobre a composição regional e tecidual da carcaça em ovinos. Quarenta e nove cordeiros machos não-castrados da raça Texel, nascidos em duas épocas (agosto e novembro), foram mantidos em regime de pastagem e abatidos com média de idade de 129 e 164 dias, respectivamente. Previamente aos abates foi feita a avaliação da produção forrageira do campo pelo método Botanal. Foram verificadas melhores condições forrageiras para os cordeiros nascidos em agosto, que apresentaram maior peso e proporção na maioria dos cortes, assim como menor proporção de músculo na paleta e perna; apresentando maior conteúdo de tecido adiposo na maioria dos cortes da carcaça. Para os cordeiros nascidos em novembro, ocorreu maior relação músculo:gordura e músculo:osso na paleta e na perna, assim como maior relação músculo:gordura no costilhar. As condições nutricionais são responsáveis pelas diferenças nos pesos e rendimentos dos cortes, assim como na composição tecidual da carcaça, em cordeiros mantidos em regime de pasto, viabilizando o uso de época alternativa de nascimentos para incrementar a oferta de animais para o abate.

The effect of alternative birth season on regional and tissue carcass composition of sheep was evaluated. Forty nine (49) Texel intact male lambs, born in two seasons (August and November), were kept under grazing and slaughtered with an average age of 129 and 164 days, respectively. Prior to slaughter forage production was measured using Botanal method. Lambs born in August had more favorable forage conditions, showing higher body weight and proportion in the majority of cuts, as well as lower proportion of shoulder and leg muscles showing higher adipose tissue content in the majority of carcass cuts. For lambs born in November, a higher muscle:fat and muscle:bone rate in shoulder and leg, as well as a higher ribcut muscle:fat rate. Nutritional conditions are responsible for differences in weights and cuts yields, as well as for the tissue carcass composition, in lambs maintained under grazing regime, making feasible the use of alternative birth periods to increase animal offer for slaughter.