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Resumo -O objetivo deste trabalho foi avaliar a infl uência de fontes protéicas sobre desempenho, características da carcaça e da carne de cordeiros confi nados, e estimar a digestibilidade do amido de rações com alta proporção de grãos. Foram distribuídos 28 cordeiros Santa Inês, em blocos completos ao acaso, de acordo com o peso vivo e a idade, no início do experimento. As fontes protéicas foram os farelos de: soja, amendoim, canola e algodão, em dietas isonitrogenadas com 90% de concentrado e 10% de volumoso (feno de coast-cross). Na determinação da digestibilidade, foram utilizados quatro borregos em delineamento experimental em quadrado latino 4x4, e a digestibilidade do amido foi estimada a partir do teor de amido fecal. Não houve diferenças (p>0,05) quanto ao consumo de matéria seca, ganho de peso vivo médio, conversão alimentar, características da carcaça e da carne, entre as fontes protéicas avaliadas. A digestibilidade do amido apresentou coefi ciente de determinação de 93%. Independentemente da fonte protéica utilizada, o teor de amido nas fezes é um indicador efi ciente na estimativa da digestibilidade do amido de dietas com alta proporção de concentrado para cordeiros.Termos para indexação: amido fecal, características da carcaça, características da carne, ovinos. Lamb performance and estimation of starch digestibility of diets with different protein sourcesAbstract -The objective of this work was to evaluate the infl uence of protein sources on feedlot lambs performance, carcass and meat characteristics, and to estimate starch digestibility of high grain diets. Twenty-eight Santa Inês ram lambs were selected in a complete randomized block design, according to body weight and age in the beginning of the experiment. Protein sources were the following meals: soybean, peanut, canola, and cottonseed in isonitrogenous diets with 90% concentrate and 10% roughage (coast-cross hay). Four ram lambs (48 kg) were used to determine starch digestibility in a 4x4 latin square design, and starch digestibility was estimated by fecal concentration of starch. There were no differences (p>0.05) for dry matter intake, average daily gain, feed conversion, carcass characteristics and meat quality, among the protein sources evaluated. Determination coeffi cient for starch digestibility was 93%. Fecal starch content is an accurate indicator of the starch digestibility estimation in lambs feeding high grain diets, independently of the protein source used.

The objectives of this experiment were to determine the effects of replacing ground corn with soybean hulls (SH) in high-concentrate diets on the growth (56-d period), carcass characteristics, and eating behavior of feedlot lambs. Sixty-four Santa Inês ram lambs (18.3 ± 2.8 kg of BW and 69 ± 5 d of age) were assigned to a randomized complete block design experiment with 8 blocks and 4 diets. The control diet contained 10% coastcross (Cynodon sp.) hay, 70% corn, and no SH (SH0) in the dietary DM. In the remaining diets, SH replaced corn at the rate of 15 (SH15), 30 (SH30), or 45% (SH45) of the original corn concentration, resulting in 0, 10.5, 21.0, or 31.4% SH in the dietary DM. Dry matter intake increased linearly (P < 0.01) when SH replaced ground corn (1.0, 1.0, 1.1, and 1.1 kg/d for SH0, SH15, SH30, and SH45, respectively). There was no effect on ADG of lambs, with values of 276, 278, 282, and 287 g for SH0, SH15, SH30, and SH45, respectively. Feed efficiency decreased linearly (P < 0.01) with SH inclusion. Carcass measures were not affected by SH as a replacement for ground corn. Eating time, expressed as minutes per day and minutes per gram of NDF, showed a quadratic effect (P < 0.05), whereas no effect was observed when expressed as minutes per gram of DM. Rumination, in minutes per day, was not influenced by dietary SH inclusion, but a linear decrease (P < 0.01) was observed when this variable was expressed as minutes per gram of NDF. Soybean hulls can replace up to 45% of the ground corn (31.4% of SH in the dietary DM) in high-concentrate diets fed to feedlot lambs without negative effects on ADG and carcass measures. The linear decrease in feed efficiency (11.6% reduction from SH0 to SH45) suggests that optimal dietary SH inclusion rates should be dictated by the relative costs of SH and corn.

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