The objective of this work was to evaluate the effects of supplementation with nitrogen and starch on the nutritional performance of grazing cattle during the rainy season. Five rumen cannulated Nellore steers, averaging 211 kg of body weight (BW), were used. Animals grazed on five signal grass paddocks. Five treatments were evaluated: control (forage only), ruminal supplementation with nitrogen at 1 g of crude protein (CP)/kg BW, ruminal supplementation with starch at 2.5 g/kg BW, supplementation with nitrogen (1 g CP/kg BW) and starch (2.5 g/kg BW), and supplementation with nitrogen (1 g CP/kg BW) and a mixture of corn starch and nitrogenous compounds (2.5 g/kg BW), thereby resulting in an energy part of the supplement with 150 g CP/kg of dry matter (DM). This last treatment was considered an additional treatment. The experiment was carried out according to a 5 ×5 Latin square design following a 2×2+1 factorial arrangement (with or without nitrogen, with or without starch, and the additional treatment). Nitrogen supplementation did not affect (p>0.10) forage intake. Starch supplementation increased (p<0.10) total intake but did not affect (p<0.10) forage intake. There was an interaction between nitrogen and starch (p<0.10) for organic matter digestibility. Organic matter digestibility was increased only by supplying starch and nitrogen together. Nitrogen balance (NB) was increased (p<0.10) by the nitrogen supplementation as well as by starch supplementation. Despite this, even though a significant interaction was not observed (p>0.10), NB obtained with nitrogen plus starch supplementation was greater than NB obtained with either nitrogen or starch exclusive supplementation. Supplementation with starch and nitrogen to beef cattle grazing during the rainy season can possibly improve digestion and nitrogen retention in the animal..

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BackgroundThere is little information in the tropics with regard the comparative understanding of how an increased nitrogen supply in the rumen or in the intestines affects efficiency of nitrogen utilization in cattle. This study evaluated the effects of supplementation with nitrogenous compounds in the rumen, abomasum, or both on intake, digestibility and the characteristics of nitrogen utilization in cattle fed tropical forage. Four rumen- and abomasum-fistulated Nellore bulls (227 ± 11 kg) were used. Four treatments were evaluated: control, ruminal supplementation (230 g/d of supplemental protein in the rumen), abomasal supplementation (230 g/d of supplemental protein in the abomasum), and ruminal and abomasal supplementation (115 g/d protein in both the rumen and the abomasum). The basal forage diet consisted of Tifton 85 hay with a crude protein (CP) level of 78.4 g/kg dry matter. Casein was used as a supplement. The experiment was conducted using a 4 × 4 Latin square.ResultsThere were no differences between the treatments (P > 0.10) with regard to forage intake. The intake and total digestibility of CP increased (P < 0.01) with supplementation. The nitrogen balance in the body increased (P < 0.01) and muscle protein mobilization decreased (P < 0.01) with supplementation, regardless of the supplementation site. The efficiency of nitrogen utilization did not differ among the treatments (P > 0.10).ConclusionsThe supplementation of cattle fed tropical forage with protein in the rumen, abomasum, or both similarly increased the nitrogen accretion in animal, which reflects improvements on nitrogen status in animal body.

ObjectiveEffects of nitrogen supplementation associated with different levels of starch on voluntary intake, digestibility, and rumen and metabolic characteristics of cattle fed low-quality tropical forage (Brachiaria decumbens hay, 7.4% crude protein, CP) were evaluated using ruminal and abomasal cannulated steers.MethodsFive European×Zebu young bulls (186 kg body weight, BW) were distributed according to a 5×5 Latin square. The following treatments were evaluated: control, supplementation with 300 g CP/d (0:1), supplementation with 300 g starch/d and 300 g CP/d (1:1), supplementation with 600 g starch/d and 300 g CP/d (2:1), and supplementation with 900 g starch/d and 300 g CP/d (3:1). A mixture of nitrogenous compounds provided 1/3 from true protein (casein) and 2/3 from non-protein nitrogen (mixture of urea and ammonium sulphate, 9:1) was used as the nitrogen supplement. In order to supply energy a unique source of corn starch was used.ResultsSupplements increased (p<0.05) dry matter intake, but did not affect (p>0.05) forage intake. There was a cubic effect (p<0.05) of starch on voluntary intake. This was attributed to the highest forage intake (g/kg BW) when using the 2:1 starch:CP ratio. Supplements increased (p<0.05) organic matter (OM) digestibility, but did not affect (p>0.05) neutral detergent fibre corrected for ash and protein (NDFap) digestibility. There was a positive linear effect (p<0.05) of the amount of starch supplemented on OM digestibility. Total NDFap digestibility was not affected (p>0.05) by the amount of supplemental starch. Ruminal ammonia nitrogen concentrations were higher (p<0.05) in supplemented animals, however, a negative linear effect (p<0.05) of amount of starch was observed. Supplements increased (p<0.05) the nitrogen balance (NB) and efficiency of nitrogen utilization. These effects were attributed to increased body anabolism, supported by higher (p<0.05) serum concentration of insulin-like growth factor 1. Increasing the amount of starch tended (p<0.06) to linearly increase the NB. In spite of this, there was a highest NB value for the 2:1 starch:CP ratio amongst the treatments with supplementation.ConclusionNitrogen supplementation in cattle fed low-quality tropical forage increases nitrogen retention in the animal’s body. An additional supply of starch increases nitrogen retention by increasing energy availability for both rumen and animal metabolism.

Resumo -O objetivo deste trabalho foi avaliar o consumo de nutrientes e o desempenho produtivo e econômico de ovinos confinados da raça Santa Inês, alimentados com dietas com diferentes taxas de inclusão de torta de macaúba. Os animais (24) foram distribuídos em delineamento de blocos ao acaso, nos tratamentos com 0, 100, 200 e 300 g kg -1 de torta de macaúba na matéria seca da dieta, em seis repetições, durante 60 dias de confinamento. A adição de torta de macaúba a taxas crescentes à dieta aumentou linearmente o consumo de proteína bruta, extrato etéreo, fibra em detergente neutro e a conversão alimentar. Não houve diferença no consumo de matéria seca, ganho médio diário e ganho de peso vivo total com a adição da torta. O tratamento com inclusão de 100 g kg -1 apresentou a melhor relação custo:benefício na avaliação das receitas bruta e líquida obtidas com a venda dos animais vivos e abatidos. A adição da torta de macaúba em até 300 g kg -1 da dieta não altera o desempenho produtivo dos animais, entretanto, a inclusão de 100 g kg -1 proporciona melhor retorno econômico.Termos para indexação: Acrocomia aculeata, confinamento, coproduto, ovinos, terminação. Performance of lambs fed with macauba pie inclusion in the dietAbstract -The objective of this work was to evaluate the nutrient uptake and the productive and economic performance of confined Santa Inês lambs fed diets with different levels of macauba pie inclusion . The animals (24) were distributed in a randomized block design, in treatments with 0, 100, 200 and 300 g kg -1 macauba pie in the diet dry matter, with six replicates during 60 days of confinement. The addition of macauba pie at increasing rates to the diet linearly increased the intake of crude protein, ether extract, neutral detergent fiber and feed conversion. There was no difference in dry matter intake, average daily gain and total live weight gain with the macauba pie addition. Diet with 100 g kg -1 macauba pie inclusion showed the best cost:benefit ratio in the evaluation of gross and net revenues from the sale of live and slaughtered animals. The addition of macauba pie up to 300 g kg -1 to the diet does not affect the animal growth performance; however, the addition of 100 g kg -1 macauba pie provides a better economic return.