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The objective of this study was to evaluate the influence of energy supplementation on associative effects between forage and concentrate supplements and on the performance of beef cattle on a tropical pasture during the rainy season. Twenty-eight Nellore bulls averaging 19 months of age and 325.2 ± 4.1 kg were allotted to a completely randomized design and distributed into four paddocks of two hectares each with a tropical pasture for 84 d. The treatments consisted of bulls on Urochloa brizantha cv. Xaraés pasture without concentrate supplementation or bulls on Urochloa brizantha cv. Xaraés pasture receiving concentrate supplementation at 15 (S15), 30 (S30) or 45% (S45) of the total digestible nutrients (TDN) requirement. All bulls had ad libitum access to mineral supplementation. The amount and chemical composition of the supplement were adjusted every 28 d. Forage and supplement intakes were evaluated in all animals using fecal markers. Crude protein: digestible organic matter ratio decreased with supplementation; consequently, the imbalance between dietary protein and energy increased. Forage intake decreased with increasing supplementation. The substitution rates of pasture for supplementary feed were 0.14, 0.33, and 0.46 for bulls from S15, S30, and S45 treatments, respectively. However, the apparent DM digestibility increased linearly with supplementation level. Supplementation improved the assimilation of ammonia-N in the rumen. Energy supplementation for Nellore bulls on tropical pastures during the rainy season provides excess energy relative to protein, resulting in a substitution effect of supplement intake on forage intake. Moreover, energy supplementation does not improve body weight gain. Protein sources should be added to supplements for balancing protein and energy levels, thereby reducing a likely substitution effect. O objetivo deste trabalho foi avaliar a influência da suplementação energética nos efeitos associativos entre a forragem e suplemento concentrado e no desempenho de bovinos de corte em pasto tropical durante o período chuvoso. Vinte e oito touros da raça Nelore com idade média de 19 meses e 325,2 ± 4,1 kg foram alocados em delineamento inteiramente casualizado e distribuídos em quatro piquetes de dois hectares cada, com pasto tropical por 84 dias. Os tratamentos consistiram de touros em pastagem com Urochloa brizantha cv. Xaraés sem suplementação concentrada e touros em pastagem de Urochloa brizantha cv. Xaraés recebendo suplementação concentrada com 15 (S15), 30 (S30) ou 45% (S45) da necessidade de nutrientes digestíveis totais (NDT). Todos os touros tiveram acesso ad libitum à suplementação mineral. A quantidade e a composição química do suplemento foram ajustadas a cada 28 dias. A ingestão de forragem e suplemento foi avaliada em todos os animais por meio de marcadores fecais. A relação proteína bruta: matéria orgânica digestível diminuiu com a suplementação, consequentemente, o desequilíbrio entre proteína e energia da dieta aumentou. O consumo de forragem diminuiu, com efeito substitutivo do consumo de pasto pelo suplemento de 0,14, 0,33 e 0,46 para touros dos tratamentos S15, S30 e S45, respectivamente. No entanto, a digestibilidade aparente da MS aumentou linearmente com o nível de suplementação. A suplementação melhorou a assimilação do nitrogênio amoniacal no rúmen. A suplementação energética para touros Nelore em pastagens com pasto tropical durante a estação chuvosa fornece excesso de energia em relação à proteína, resultando em um efeito de substituição do consumo de forragem por suplemento. Além disso, a suplementação energética não melhora o ganho de peso corporal. Fontes de proteína devem ser adicionadas aos suplementos para equilibrar os níveis de proteína e energia, diminuindo um provável efeito de substituição.

This study aimed to evaluate the effects of levels of concentrate supplement and dietary lipids on the nutritional characteristics, metabolic parameters, and performance of Nellore bulls grazing tropical pasture. Twenty-seven Nellore bulls were allotted to 2 × 2 completely randomized factorial design with two levels of supplementation and two levels of dietary lipids. The concentrate supplement was fed at 4 g kg-1 BW (low supplementation) and 8 g kg-1 BW (high supplementation), whereas the dietary lipid content was 28 g of ether extract (EE) g-1 on a dry matter basis (DM) (low-lipid diet) and 42 g EE kg-1 DM (high-lipid diet). There was no interaction between the level of concentrate supplement and dietary lipid content on all studied variables. High levels of supplementation led to shorter grazing time and reduced forage dry matter intake (DMF). On the other hand, the DM intake increased with increasing levels of concentrate supplement, with no significant effects on DM digestibility. The dietary lipid content did not affect forage and DM intakes. However, the digestibility of DM and neutral detergent fiber (NDF) were lowest in high-lipid diets. Bulls receiving high levels of supplementation had higher average daily gains than low-supplemented animals. Neither the amount of concentrate supplement nor the dietary lipid content affected the hot carcass yield and carcass weight. Carcass fat deposition was greater in bulls fed high-lipid diets than in animals receiving low-lipid diets. The effects of the level of concentrate supplement and dietary lipid content on the nutritional characteristics and performance of grazing beef cattle are independent. Concentrate supplementation at 8 g kg-1 BW increases cattle performance but decreases forage utilization. Diets containing 42 g EE kg-1 DM reduces the digestibility of dry matter and fiber fractions, but increases backfat thickness. Este estudo teve como objetivo avaliar o efeito da quantidade de suplemento concentrado e da concentração de lipídios na dieta, sobre as características nutricionais e metabólicas e o desempenho de touros Nelore em pastagem tropical. Vinte e sete touros Nelore foram distribuídos em esquema fatorial 2 x 2 com dois níveis de suplemento e dois níveis de lipídios alimentares). A quantidade de suplemento concentrado foi de 4 g kg-1 de PC (baixo suplemento) e 8 g kg-1 de PC (alto suplemento), enquanto os teores de lipídios dietéticos foram de 28 g de extrato etéreo (EE) g-1 de matéria seca (MS) (dieta com baixo lipídios) e 42 g de EE kg-1 de MS (dieta com alto lipídios). Não houve interação entre a quantidade de suplemento concentrado e o teor dietético de lipídios para todas as variáveis analisadas. Os altos níveis de suplemento reduziram o tempo de pastejo e consumo de matéria seca de forragem (MSF). Por outro lado, o consumo MS aumentou com as maiores quantidades de suplemento concentrado, sem qualquer efeito sobre a digestibilidade da MS. O teor de lipídios não afetou o consumo de forragem e MS. No entanto, a digestibilidade da MS e da fibra detergente neutro (FDN) foram mais baixas para as dietas com elevado teor de lipídios. Os touros que receberam níveis elevados de suplementos obtiveram maior ganho médio diário. Nem a quantidade de suplemento concentrado, nem o teor dietético de lipídeo foram influenciaram no rendimento e no peso da carcaça quente. Os touros que receberam alto teor dietético de lipídio, apresentaram maior deposição de gordura na carcaça. Os efeitos do nível de suplemento concentrado e do teor de lipídios da dieta sobre as características nutricionais e desempenho de bovinos de corte em pastejo são independentes. A oferta de 8 g kg-1 de PC de suplemento de concentrado aumenta o desempenho dos bovinos, mas diminui a utilização de forragens. O conteúdo lipídico de 42 g de EE kg-1 de MS reduz a digestibilidade da matéria seca e fibras, mas aumenta a deposição de gordura subcutânea.

Balancing diets for protein affects both protein and energy use efficiency in cattle. This study aimed to evaluate the effects of dietary protein level on intake, digestibility and energy expenditure in Holstein heifers. Four Holstein heifers with a mean BW of 266.5 ± 10.7 kg were distributed in a 4 x 4 balanced Latin square design. Each period was comprised of 14 d for adaptation and 6 d for samplings. The heifers were fed diets with 9, 12, 15 and 18% of crude protein (CP). Total feces and urine were collected. Rumen fluid was collected at 2, 4, 6 and 8 h after feeding. The energy expenditure was evaluated at 6 a.m., 12 a.m., 6 p.m. and 12 p.m. by a closed-circuit mask technique. The intake of dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) were similar between treatments (P > 0.05). Although the NDF digestibility was not changed (P > 0.05), the digestibilities of DM, OM, CP, non-fibrous carbohydrates, and total digestible nutrients increased linearly (P < 0.05) with increasing CP levels in the diet. Urinary urea nitrogen excretion and nitrogen retained increased linearly (P < 0.01) with increasing CP levels. Dietary CP levels did not affect (P =0.53) energy expenditure in heifers. Ruminal ammonia-nitrogen concentration peaked at 2-4 h after feeding. Increasing dietary CP levels from 9 to 18% does not affect feed intake and energy expenditure in heifers. However, it improves the digestibility of OM and nitrogen retention. O balanceamento das dietas proteicas afeta tanto a eficiência no uso de proteínas quanto a eficiência no uso de energia em bovinos. Este estudo teve como objetivo avaliar os efeitos dos níveis de proteína na dieta sobre consumo, digestibilidade e gasto de energia em novilhas Holandesas. Quatro novilhas Holandesas com um peso corporal (PC) médio de 266,5 ± 10,7 kg foram distribuídas em delineamento quadrado latino 4 x 4. Cada período era composto de 14 d para adaptação e 6 d para amostragens. As novilhas foram alimentadas com 9,12,15 e 18% de proteína bruta (PB). Fezes e urina totais foram coletadas. O líquido ruminal foi coletado às 2, 4, 6 e 8 h após a alimentação. O gasto de energia foi avaliado às 6h, 12h, 18h e 12h por uma técnica de máscara de circuito fechado. O consumo de matéria seca (MS), matéria orgânica (MO) e fibra em detergente neutro (FDN) foram similares entre os tratamentos (P > 0,05). Embora a digestibilidade do FDN não tenha sido alterada (P > 0,05), a digestibilidade de MS, MO, PB, carboidratos não-fibrosos e nutrientes digestíveis totais aumentou linearmente (P < 0,05) com o aumento dos níveis de PB na dieta. A excreção de uréia urinária e o nitrogênio retido aumentaram linearmente (P < 0,01). Os níveis de PB na dieta não afetaram (P = 0,53) o gasto de energia em novilhas. A concentração de nitrogênio amoniacal atingiu o pico em 2-4 h após a alimentação. O aumento dos níveis dietéticos de PB de 9 para 18% não afeta o consumo de ração e o gasto de energia em novilhas. Entretanto, melhora a digestibilidade da MO e a retenção de nitrogênio.

The objective of this study was to evaluate the effects of the amount of balanced protein/energy supplement adjusted according to the protein content of the pasture on intake, digestibility, and performance of young bulls managed on tropical pasture. Thirty-six crossbred bulls (½ Angus × ½ Nellore) averaging 8 months of age and 217.2 ± 4 kg were distributed to eight 1-hectare paddocks with tropical grass. The treatments were based on the amounts of balanced protein/energy supplement (0, 2.8, 5.5 and 7.4 g/kg of body weight - BW). The amounts of supplement were chosen to achieve dietary protein levels of 110, 130 and 150 g/kg of dry matter (DM). The increase of supplementation had a positive linear pattern (P 0.05) with supplementation. The apparent digestibility of DM, OM, CP and NDF were not affected (P > 0.05) by increasing supplement amounts. Conversely, the grazing time decreased linearly (P = 0.022) with increasing supplementation. Moreover, a linear increase in the final body weight (P = 0.002) and average daily gain (P = 0.002) and, a linear decrease in the efficiency of supplement use (P = 0.021) were observed with increasing supplementation. Increasing the amount of balanced protein/energy supplementation increases the DM intake, digestibility and animal performance with no substitution effect on forage intake.

The aim of this study was to evaluate the effect of supplementation of pig diets in the growth and termination phases with different calcium sources. In experiment I, 36 whole males were distributed in randomized blocks in six groups, with six replications. A basal diet was formulated to meet the animals' nutritional requirements except for calcium (0.09%), and the sources evaluated (calcitic limestone, monodicalcium phosphate, calcinated bone flour, and oyster flour) replaced the basal diet to provide 0.59% of total calcium. To determine the endogenous calcium, a diet containing low calcium (0.019%) was given simultaneously to another group of animals. Feces and urine were collected for determination the coefficients of apparent and true digestibility. In experiment II, 160 piglets were distributed in randomized blocks in four treatments, with five replications and four animals per experimental unit. Carcass and performance parameters, calcium concentration in bone and serum, and bone parameters were evaluated. The data were submitted to analysis of variance and factorial. The calcium source did not influence the digestibility coefficients determined by total collection (P 0.05). The digestibility of Ca from oyster flour estimated by collection with an indicator was higher than that from the other sources (P 0.05). Calcium sources did not interfere in the evaluated parameters (P 0.05). The sources studied in this work can be used to supplement growing pigs' diets.