Dietas de alto grão no comportamento, desempenho e qualidade da carne de novilhos confinados

Abstract

This study aimed to assess the feasibility of the use of soybean hulls and/or white oat grain in the diet of feedlot steers fed exclusively with concentrate and its response on performance, ingestive behavior, non-carcass components and meat and carcass characteristics. We used thirty three crossbred steers with Charolais or Nellore predominance, with average age and weight of 20 months and 269.72 kg. The animals were randomly distributed in the treatments, blocked according to their genetic predominance, and kept in individual pens. Diets were isonitrogenous, being the treatments: Soybean hulls; White oat grain and the Mixture (equal parts of soybean hulls and oat grain), plus limestone and protein nucleus. There was no difference (P> 0.05) among treatments for dry matter intake (7.42 kg day-1; 2.23% BW). Despite the similar dry matter intake, steers of the mixture treatment had greater weight gain compared to the soybean hulls treatment (1.300 vs. 0.972 kg day-1), but these two treatments were similar to the oat grain (1.203 kg-1 day). Animals fed soybean hulls remained longer time in total idle (1,164 minutes) compared with those fed the mixture (1.061 min), which in turn, remained longer in idling than animals fed oat grain (971 min) (P <0.05); for the total rumination time we observed a contrary behavior, 69 min, 217 min and 343 min, respectively (P <0.05). Carcass weights and yields of hot (65.99%) and cold carcass (64.45%) of the steers, expressed in empty body weight were not affected by treatments (P> 0.05). There was higher internal fat in the abdominal cavity in steers from the oat grain treatment in relation to others (16.22 vs 20.58 kg; 4.93 vs 6.15 kg 100 kg-1 empty body) (P <0.05). The absolute and relative weights of all the internal organs and external components of the steers was similar (P> 0.05). Steers fed oat grain and the mixture had greater blood volume in relation to steers fed soybean hulls (3.53 vs 2.80 kg 100 kg-1 of empty body). Carcass quantitative traits and physical composition, with exception of forequarter, muscle and fat percentage, were not affected (P>.05) by the treatments. The use of diets with 100% concentrate are technically viable for steers fed diets based on oat grain or the mixture. The high contend of soluble neutral detergent fiber in treatment based on soybean hulls, is not sufficient to promote adequate ingestive behavior (rumination time) of steers compared to the other treatments. Diets based exclusively on concentrate do not influence the empty body weight of steers feedlot finished and promote similar (P>.05) meat qualitative characteristics.