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Productive performance of crossbreds Nellore beef heifers, in the growing stage receiving different supplement levels for three months grazing Brachiaria decumbens pasture were evaluated. The area was divided in five paddocks of 2.5 ha, with dry matter availability and potentially of dry matter digestible of 3.85 and 2.12 t/ha, respectively. Forty beef heifers of 191 ± 3.99 kg initial weight and 8.5 ± 0.15 months of age were assigned in a completely randomized experimental design with five treatments, and four supplementation levels. Mineral mixture (MM) (60 g/day) and multiple supplements, formulated to supply different supplementation levels in the amounts of 0.5, 1.0, 1.5 and 2.0 kg/animal more MM (60 g/day) were evaluated. The supplement had 300 g of crude protein/kg. Animals not responded significantly (P > 0.05) to the use of multiples supplements to final body weight. However, the heifers than received supplement won more weight (P £ 0.01) (372 g vs. 92g of average daily gain), in addition to highers (P £ 0.01) serum N-urea levels (20.14 vs. 12.09 mg/dL), when compared with heifers fed diets supplied only with mineral mixture. In conclusion, increasing the amount of protein supplement during the dry season, increased of performance of beef heifers. However, despite increase productive performance and intake of energy during dry season, additional higher levels of supplementation resulted in lower increment in growth.

The objective of this study was to estimate requirements of energy, protein and macrominerals of young Nellore/Holstein crossbreds bulls supplemented on pastures of Brachiaria decumbens Stapf. Thirty-five young bulls, at 8.53±0.18 months of age and with initial body weight of 230.6±6.1 kg were used. Ten animals were slaughtered as reference, in different weight range, and the other animals were slaughtered at the end of the experimental period. For estimate of net energy requirements for weight, a regression equation between log of retained energy (RE) and log of empty body weight gain (EBWG) was constructed. Net requirements of Ca, P, Mg, Na and K were determined by the equation Y' = a.b.Xb-1, in which a and b represent the intercept and the coefficient of equation of prediction of macrominerals in body content, respectively. Requirements of metabolizable energy for maintenance (MEm) were obtained from retained energy in function of metabolizable energy intake (MEI). The requirements of MEm of Nellore/Holstein crossbreds young bulls on pasture was 125 kcal/EBW0.75/day. The efficiency of ME utilization for maintenance (km) of grazing Nellore/Holstein crossbred young bulls was 0.58 and 0.24 for gain. The total metabolizable protein requirements for an animal with 400 kg and with average daily gain of 1.0 kg, were 638.36 g/day. The dietetic requirements of Ca and P for an animal with 400 kg BW were 0.49 and 0.21% of DM, respectively. Daily metabolizable energy requirement for maintenance of grazing Nellore/Holstein crossbred young bulls was 11.6% greater than the values found for cattle in feedlot in Brazil (112 kcal/kg EBW0.75).

The objective of this experiment was to study the effects of different levels of supplementation on the performance, intake, digestibility, pH and rumen ammonia concentration in growing bulls grazing Brachiaria decumbens Stapf. pasture, during the dry-rainy transition season. For evaluation of performance, intake and digestibility, it was used 25 non-castrated steers at 11 months of age and initial average body weight of 270 kg, grouped in five plots of five animals each, following a completely randomized design. Each plot received one of the following feeding treatments: mineral mixture and supplement at the proportion of 0.5, 1.0, 1.5 and 2.0 kg/animal/day, corresponding to 0.18, 0.36, 0.54 and 0.72% of the average body weight of the animals. The area designated for the animals was constituted of five 2.0-ha paddocks. For the evaluation of the pH and rumen ammonia concentration, five crossbred non-castrated steers were used, with average body weight of 240 kg, fistulated in the esophagus, rumen and abomasum, disposed in a 5 × 5 Latin square, with five treatments and five experimental periods. Animal performance behaved in a positive linear manner according to the supplementation levels, responding with an increase of more than 80% on weight gains of the animals. Intakes of total and pasture dry matter (DM), organic matter and neutral detergent fiber were not influenced by supplementation. Intakes of crude protein, non-fibrous carbohydrates, ether extract and total digestible nutrients as well as nutrient digestibility and rumen ammonia concentration showed a positive linear pattern in response to supplementation levels. Increasing levels of concentrate supplementation influence positively the performance of bulls growing on pastures during the dry-rainy transition season. Objetivou-se estudar os efeitos de diferentes níveis de suplementação sobre o desempenho, o consumo, a digestibilidade, o pH e a concentração de amônia ruminal em bovinos recriados em pastagem de Brachiaria decumbens Stapf. durante o período de transição seca-águas. Para avaliação do desempenho, do consumo e da digestibilidade, foram utilizados 25 novilhos não-castrados com idade e peso médio iniciais de 11 meses e 270 kg, divididos em cinco lotes de cinco animais, segundo um delineamento inteiramente casualizado. Cada lote recebeu um dos seguintes complementos alimentares: mistura mineral; e suplemento na proporção de 0,5; 1,0; 1,5 e 2,0 kg/animal/dia, correspondentes a 0,18; 0,36; 0,54 e 0,72% do peso corporal médio dos animais. A área destinada aos animais foi constituída de cinco piquetes de 2,0 ha. Para a avaliação do pH e da concentração ruminal de amônia, foram utilizados cinco novilhos mestiços não-castrados, com peso médio de 240 kg, fistulados no esôfago, rúmen e abomaso, dispostos em quadrado latino 5 × 5, com cinco tratamentos e cinco períodos experimentais. O desempenho dos animais comportou-se de forma linear positiva de acordo com os níveis de suplementação, refletindo em aumento de mais de 80% no ganho de peso dos animais. Os consumos de matéria seca (MS) total e do pasto, de matéria orgânica e de fibra em detergente neutro não foram influenciados pela suplementação. Os consumos de proteína bruta, carboidratos não fibrosos, extrato etéreo e nutrientes digestíveis totais, assim como a digestibilidade dos nutrientes e a concentração de amônia ruminal, apresentaram comportamento linear positivo em resposta aos níveis de suplementação. Níveis crescentes de suplementação concentrada influenciam positivamente o desempenho de bovinos recriados em pastejo no período de transição seca-águas.

The objective of this work was to determine macromineral requirements by Zebu steers grazing Brachiaria decumbens supplemented with concentrate. It was used 24 non-castrated steers, at an average age of 7 months and at initial average weight 180 kg. Eight control animals were slaughtered for determining initial body composition. The 16 remaining animals were divided in four four-animal plots, in a complete random design. Each plot received mineral mixture or supplements at the levels 0.75; 1.50 or 2.25 kg/animal/day. The right half-carcass of eight animals, two per group, was dissected in muscle, fat and bones and all body constituents were weighted for determination of empty body weight and body composition. Net requirements of calcium and phosphorus for an animal at 400 kg body weight were 11.13 g and 5.40 g, respectively. To estimate dietary requirements of maintenance and after, sum them to dietary requirements for gain in order to obtain total dietary requirements, it was adopted endogenous losses and bioavailability present in literature for each mineral macroelement. Total dietary requirement for calcium, phosphorus, magnesium, sodium and potassium for a 400-kg BW animal with 1.0-kg daily weight gain were 34.59; 17.36; 7.82; 5.19 and 41.11 g/day, respectively. Macromineral requirements by beef cattle under pasture supplementation are similar to those recommended by BR-Corte for beef cattle in feedlots.