A series of experiments were conducted to investigate the effects of adding an exogenous proteolytic enzyme (EPE) on the growth performance of beef steers fed growing and finishing diets containing 30% dried distillers grains with solubles (DDGS; Exp. 1), and results corroborated by in vitro ruminal fermentation in continuous cultures (Exp. 2). In Exp. 1, 48 group-penned Angus crossbred steers were randomly assigned to 2 treatments (n = 6) in a completely randomized design: DDGS TMR (DT) without and with EPE (27 mg of azocasein hydrolyzed/min/kg DM TMR). The addition of EPE during the growing phase increased DMI (P = 0.02), but had no effects on final BW, BW change, ADG, and G:F. Adding EPE during the growing phase decreased NDF digestibility, whereas the digestibility of DM, CP, and ADF were not affected. There was a tendency for both ADG (P = 0.09) and final BW (P = 0.11) to increase during the finishing phase without affecting BW change and G:F. As opposed to the growing phase, EPE increased digestibility (P < 0.04) of DM, CP, NDF, and ADF. In Exp. 2, 4 dietary treatments were assessed in continuous cultures; non-DDGS TMR (NDT) or DT finishing beef steer diet was combined without or with EPE in a 2 × 2 factorial design. The DT was the same diet used as the finishing diet in Exp. 1, and dose rate of EPE was the same as Exp. 1. Feeding the DT increased total VFA concentration (P = 0.01) which corresponded with a decreased (P < 0.01) pH compared with the NDT diet (5.8 vs. 6.0) regardless of EPE supplementation. Supplementing EPE tended to increase (P = 0.07) the total VFA concentration in both diets, but only increased digestibility of DM, OM, and NDF when added to the DT diet (P < 0.05), leading to tendencies on TMR × enzyme interaction (P < 0.10). Addition of the EPE product assessed in this study resulted in positive responses in Exp. 1 and 2 when added to finishing beef steer diets, and thus it is clear that use of protease enzyme products may be more effective in high concentrate diets such as finishing beef steer diets containing DDGS.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The aim of this work was to study the use of whole dry white oat grain (Avena sativa), soybean hulls (Glycine max L.), and the mixture of these ingredients (1:1), provided in two ways: with or without a roughage source on the diet. Sixty- eight male castrated steers, Charolais x Nelore crossbred, with initial average age of 20 months were used, distributed in a factorial scheme 3 x 2, with three energetic sources on the concentrate (white oat grain; soybean hulls and the mixture of these ingredients) and two ways of provision (with or without roughage). The roughage used was sorghum silage (Sorghum bicolor (L.) Moench), with roughage: concentrate of 50:50, based on DM. The ingestive behavior characteristics and the animal's performance response were measured and compared. The final weights of the steers did not differ statistically. The daily average gain of the mixture source (1.167 kg) was superior (P<0.05) to the soybean hulls (0.940 kg), being the oat grain intermediate (1.061 kg). It was observed higher (P<0.05) intake of dry matter and neutral and acid detergent fiber on the diets that contained roughage. Animals fed without roughage presented in the average better (P<0.05) feed conversion (6.291 kg) in relation to the animals fed with roughage (8.578 kg). Independently of the energetic source tested, steers fed with roughage remained more time (P<0.05) eating (4.23 h) and ruminating (7.88 h), compared to the ones fed without roughage (2.68 and 3.52 h, respectively). Steers fed with the energetic sources of oat grain and mixture, were more efficient in the dry matter intake (DM) when fed without roughage. On the average, steers fed without roughage were more efficient in the intake of neutral detergent fiber (NDF) and more efficient in the rumination of NDF. Steers fed with or without roughage presented difference (P<0.05) for the total chewing time (13.13 and 6.19h), for the number of ruminal bolus per day (502 and 184), and for the number of rumination chews (30,774 and 11,637, respectively). Steers from the soybean hulls energetic source chewed a few (P<0.05) number of times per ruminal bolus when fed without roughage (41.63), compared to the ones fed with roughage (62.66). / Objetivou-se neste trabalho, estudar a utilização do grão de aveia branca (Avena sativa) na forma inteiro seco, e a casca do grão de soja (Glycine max L.), e a mistura desses ingredientes (1:1), fornecidos de duas formas: com ou sem a fonte de volumoso na dieta. Foram utilizados 68 novilhos cruzas Charolês x Nelore, machos castrados, com idade média inicial de 20 meses, distribuídos em um esquema fatorial 3 x 2, com três fontes energéticas no concentrado (grão de aveia branca; casca do grão de soja e a mistura desses ingredientes) e duas formas de fornecimento (com ou sem volumoso). O volumoso utilizado foi silagem de sorgo (Sorghum bicolor (L.) Moench), com uma relação volumoso:concentrado de 50:50, com base na MS. Foram mensuradas e comparadas as características do comportamento ingestivo e respostas de desempenho dos animais. Os pesos finais dos novilhos não diferiram estatisticamente. O ganho médio diário da fonte energética Mistura (1,167 kg) foi superior (P<0,05) a Casca de Soja (0,940 kg), sendo Grão de Aveia intermediária (1,061 kg). Observou-se maiores (P<0,05) consumos de matéria seca e fibra em detergente neutro e ácido nas dietas que apresentavam volumoso. Animais alimentados sem volumoso apresentaram melhor (P<0,05) conversão alimentar (6,291 kg) em relação aos animais alimentados com volumoso (8,578 kg). Independente da fonte energética testada, novilhos alimentados com volumoso desprenderam mais tempo (P<0,05) se alimentando (4,23 h) e ruminando (7,88 h), comparados aos sem volumoso (2,68 e 3,52 h, respectivamente). Novilhos alimentados com as fontes energéticas Grão de Aveia e Mistura foram mais eficientes nos consumos de matéria seca (MS) quando alimentados sem volumoso. Na média os novilhos alimentados sem volumoso foram mais eficientes no consumo de fibra em detergente neutro (FDN), e mais eficientes na ruminação da FDN. Novilhos alimentados com e sem volumoso apresentaram diferença (P<0,05) para o tempo de mastigação total (13,13 e 6,19h), no número de bolos ruminais por dia (502 e 184), e no número de mastigadas merícicas (30.774 e 11.637, respectivamente). Novilhos da fonte energética Casca de Soja mastigam em menor (P<0,05) número de vezes por bolo ruminal quando alimentados sem volumoso (41,63), em comparação aos alimentados com volumoso (62,66).