The objective ofthis work was to evaluate the effect of using multiple supplements with differentlevels of cottonseed meal 38% on intake, total apparent digestibility of dietarycomponents, efficiency of microbial synthesis and productive performance ofbeef heifers in Brachiaria decumbens pasture during the rainy season.It was used 25 Nellore heifers and 10 crossbred heifers with predominance ofZebu breed at 16 months of age and with 249.8 ± 0.6 kg of body weight. It wasused a complete random experimental design with five treatments and seven replicates.Supplements contained approximately 30% of crude protein (CP) and soybean mealreplaced by cottonseed meal 38% at the levels 0; 33; 67 and 100%, (CS0,CS33, CS67 and CS100, respectively) evaluatedin relation to a control group, which received only mineral mixture (MM) adlibitum. Daily weight gain was 397, 546, 570, 525 and 542 g, respectively,for the groups MM, CS0, CS33, CS67 and CS100.There was no effect of the levels of cottonseed meal 38% on daily weight gain,which differed among animals fed supplement and control group, however. Intakesof crude protein and non-fibrous carbohydrates (NFC) in kg/day were greaterin groups under supplementation. Coefficients of total apparent digestibilityof CP and NFC were greater in animals fed supplements in relation to the controlgroup. Increase on the replacement level of soybean meal by cottonseed mealhad a positive linear effect on coefficients of total apparent digestibilityof DM, organic matter and CP. There was no difference on microbial efficiency,expressed as g of crude protein per kg of TDN consumed by the animals undersupplements and the ones of the control group, neither it was observed differenceamong levels of replacement of soybean meal by cottonseed meal. The use of cottonseedmeal 38% replacing soybean meal in the diet does not harm performance of grazingbeef heifers.
