R. Bras. Zootec.01/Dec/2007;36(6 Sup..):2082-91.
Effect of the protein source and physical processing of the concentrate on the finishing of feedlot young bulls and environmental impact of dejections
The objective of this research was to evaluate the effect of two protein ingredients of the diet (soybean and cottonseed meals) and two physical process of the concentrate (grounded and extruded) upon the finishing of 16 Canchim young bulls. It was evaluated also the nutrients excretion in feces and biogas production potential. The animals were 12 month-year-old, with initial 315 kg BW, and they were confined in individual pens for 147 days, being the first 35 days of adaptation. The roughage used was corn silage and the forage:concentrate rate was 50:50, on dry matter basis. The results were analyzed in a total randomized design, in a 2 × 2 factorial arrangement (protein source x physical process). There was effect of protein source upon the body weight gain (1.50 and 1.35 kg/day with soybean and cottonseed meal, respectively), feed conversion (4.73 and 5.31 kg DM intake/kg weight gain, respectively) and protein efficiency (1.78 and 1.59 kg weight gain/kg CP intake, respectively). There was no difference among treatments for DM, loin eye area and subcutaneous fat thickness, evaluated by ultra-sound. The nutrient balance was similar among treatments for DM, NDF and ADF, but protein source caused differences in CP balance. Among the macro and microminerals determined in feces, P and Mg contents were different among protein sources, and extrusion increased Ca content, with means of 0.39 and 0.43 g/100 g dejections dry matter, respectively for grounded and extruded concentrate. The dejections produced biogas effectively from 70th to 200th days.