The aim of this study was to evaluate the effect of increasing concentrate supplementation levels on the intake, nutrient digestibility, and performance of crossbred steers during the dry period of the year. The experiment was developed on Princesa do Mateiro farm, in the municipality of Ribeirão do Largo, located in the southwest region of Bahia State, Brazil. Forty uncastrated male crossbred (½ Holstein-Zebu) steers with an average body weight (BW) of 232.55 ± 24.97 kg were distributed into four treatments in a completely randomized design with ten replicates. The animals were managed in an experimental area formed by Brachiaria brizantha cv. Marandu, in an intermittent grazing system. Treatments consisted of the following supplementation levels: 0.2% BW, with 60% crude protein (CP); 0.3% BW, with 40% CP; 0.4% BW, with 30% CP; and 0.5% BW, with 24% CP. The intakes of forage dry matter in kg/day and %BW and neutral detergent fiber corrected for ash and protein (NDFap) in %BW decreased linearly, whereas the intake of non-fibrous carbohydrates corrected for ash and protein in kg/day and average daily gain increased linearly. Therefore, the use of supplementation at 0.5% BW (24% crude protein) to provide gains of up to 0.500 kg/day is recommended for grazing steers during the post-weaning period in the dry season of the year.

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ResumoObjetivou-se avaliar a ingestão de matéria seca, digestibilidade dos componentes da dieta, desempenho, conversão alimentar, características de carcaça e aspectos econômicos da inclusão de glicerina com baixa pureza na suplementação de bovinos terminados em pastagem com Brachiaria decumbens. Utilizou-se 35 bovinos machos, não castrados, com predominância da raça Nelore, com peso corporal médio inicial de 428,0 ± 32,11 kg, distribuídos em delineamento inteiramente casualizado, com cinco tratamentos e sete repetições. Os tratamentos consistiram de teores de inclusão da glicerina (0, 3, 6, 9 e 12%) na matéria seca (MS). Os animais foram pesados a cada 28 dias para avaliação do ganho de peso médio diário (GMD) e ajuste da ração. Ao final do experimento os animais foram pesados para obtenção do peso corporal médio final (PCF) e abatidos para a avaliação do rendimento de carcaça quente (RCQ) e das características de carcaça. A análise econômica foi realizada em relação ao ganho de peso em arrobas, a fim de se verificar a viabilidade do uso das rações com cinco teores de glicerina, sem considerar os demais custos fixos e operacionais. Houve efeito linear crescente (P<0,05) dos teores de glicerina sobre a ingestão e coeficiente de digestibilidade do extrato etéreo e GMD. Efeito linear decrescente (P<0,05) sobre os coeficientes de digestibilidade da fibra em detergente neutro (CDFDN), proteína bruta (CDPB) e conversão alimentar (CA). Não foram observados efeitos (P<0,05) da inclusão da glicerina sobre as características de carcaça avaliadas. A inclusão da glicerina reduziu o custo de produção de arroba de carne quando o preço desse ingrediente representou até 70% do preço do milho. A glicerina de baixa pureza pode ser incluída na dieta de bovinos não castrados em terminação a pasto com melhoria do desempenho e aumento dos benefícios econômicos. Palavras-chave: Alimentos alternativos, glicerol, pecuária de corte, rentabilidade, suplementação AbstractThis study aimed to evaluate the dry matter intake, digestibility of diet components, performance, feed conversion, carcass characteristics and economics aspects of inclusion with low purity glycerin

The search to find food alternatives for corn and feeding alternatives that reduce the cost of production has been constant. The use of oleaginous grains to produce ethanol and biodiesel has produced an excess of byproducts, especially biodiesel which produces crude glycerin. The objective of this study was to evaluate the effect of including crude glycerin on the ingestive behavior of crossbred heifers supplemented with pasture. Thirty-six crossbred heifers with an initial mean weight of 301.5 ± 31 kg were distributed in a completely randomized design with four treatments and nine replicates per treatment. The animals were kept in a Brachiaria brizantha (Hochst. ex A. Rich.) Stapf 'Marandu' pasture in a rotational-grazing system. The treatments tested were 0.0%, 3.33%, 6.66%, and 9.99% crude glycerin included in total DM to replace corn (Zea mays L.) Including crude glycerin reduced the time for grazing and eating at the trough and increased idle time. Rumination was quadratically influenced. Eating time (min kg -1 DM and neutral detergent fiber [NDF]) was reduced, while rumination time (min kg -1 DM and NDF) was quadratically affected by adding glycerin. The variables, time spent per ruminated bolus and the number of chews per day, were not affected. The number of boluses per day showed a quadratic effect. The number of grazing, idle, ruminating, and eating at the trough periods were not affected by including crude glycerin; means were 15.1, 24.9, and 13.3 and 3.71 periods d -1 , respectively. Feed and rumination efficiency (kg h -1 DM and NDF) increased when crude glycerin was included in the diet. Including crude glycerin promotes feed and rumination efficiency in grazing heifers.

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