Evaluación del uso de subproductos agroindustriales y promotores de crecimiento sobre novillos en pastoreo

Meat livestock farming in Costa Rica must be directed towards profitable, carbon neutral and sustainable production without detriment to the efficiency of the production process.The aim of this investigation was todetermine the effect of the use of two agroindustryby-products (dehydrated citrus pulp and Africanblack palm coconut meal) as energy supplements and three growth stimulants(zeranol (I1),estradiol(I2), and trenbolone acetate + estradiol(I3)) on daily weight gain (DWG), final live weight at farm (FLWF), transport loss (TL), hot carcass weight (HCW) and carcass yield (CY). 84 steerswere usedin two genetic groups (zebu and F1crosszebu*european) in rotational grazing of mombasa grass (Panicum maximum), for dry and rainy season. Addition of a by-product did not have effect (P >0.05) on the DWG, FLWF, HCW and CY. However, there was a statistically significant effect on TL. Thepercentage of weight lost during transport was lower for the two rations with agroindustryby-products.The DWG was higher (P <0.05) in the treatment with trenbolone + estradiol (I3) and zeranol (I1) than treatment with estradiol (I2) and control. TheCYwas greater inthegroupwith I3(58.28%) than controlgroup(54.55%). The use of the growth stimulants (I1, I2, I3)did have a significant effect (P <0.05) on HCW, and in all treatment were obtained heavier carcass than control group. There was no significant effect (P >0.05) ofbreed composition on the evaluated variables. In general, the DWGpresented in the dry season (1.22 kg·day-1) was higher than rainy season (0.91 kg·day-1). This performance was presentedfor FLWF and HCW (dry: 523.10 kg and 278.27 kg, rainy: 486.00 kg and 259.32 kg). There was no difference between seasonsforTL.The use of nutritional and non-nutritional supplements improves the productive performance of cattle under grazing conditions