This study aimed to evaluate the replacement of soybean meal with peanut cake in the concentrate of steer diets through intake behavior and physiological responses. Five steers, arranged in a 5 x 5 latin square design were used. The diets were composed of Tifton hay, ground corn, soybean meal and peanut cake, made from zero (100% soybean meal), 25, 50, 75 and 100% replacement for peanut cake in the concentrate. The levels of peanut cake did not influence (P>0.05) the intake and rumination efficiencies of dry matter and fiber in neutral detergent. Regarding the behavioral activities, the only parameter that observed a substitution effect was the number of idle periods in the morning shift (P<0.05) which had an increasing linear effect. The rate of salivary secretion and the particle breakdown were similar, because there was no effect (P>0.05) of the diets on the chewing characteristics. As there was no effect (P>0.05) of the diets on the respiratory rate, heart rate and rectal temperature, the endogenous heat produced by rumen fermentation was equivalent. The peanut cake, by containing aflatoxin, when provided in high roughage x concentrate rate, can replace soybean meal in the steers' diet because it causes similar intake behavior and physiological responses.
behavioral activities; physiological parameters; ruminant animals; oleaginous plants cakes