Desempenho, características de carcaça e de carne de novilhos Nelore alimentados com diferentes fontes de energia em confinamento

Abstract

t was evaluated the productive efficiency, carcass and meat traits of 48 Nellore bulls with initial age of 32 months and average live weight of 355.0 kg; divided into 4 treatments, MGI whole corn grain and pelleted supplement, SCMM - elephant grass silage (SC), soybean meal, urea, mineral mixture (RC) and ground corn grain, SCPC - SC with RC and citrus pulp; SCMF - SC with RC and corn flakes. It was calculated the average daily gain (ADG) of carcass, dry matter intake (DMI), feed conversion ratio (FCR = DMI / ADG), feed cost per arroba of the diets, urinary excretion of creatinine (CRE), allantoin (ALA), uric acid (ACU), total purine (PUR), allantoin:creatinine ratio, total purine:creatinine, microbial nitrogen (N mic), microbial proteins (P MIC) and blood parameters. Animals on MGI presented lower ADG and DMI (% BW) when compared to others (P<0.05), with values of 0.80; 0.93; 0.90; 0.98 kg / day for ADG and 1.77; 2.35; 2.33; 2.33% in diets for DMI MGI, SCMF, SCPC and SCMM, respectively. The FCR differed between MGI and SCPC, with values of 5.60 and 6.65, respectively. The SCMM diet resulted in lower feed costs (P <0.05) (R$ 73.01) whereas the highest was observed for SCMF (R$ 117.58). Mean values of fat depth, rib eye area, shear force, total cooking losses and carcass yield were 4.97 mm, 74.71 cm2, 57.37 N, 26.82% and 52.0%, respectively. The excretion of CRE, AL, AU, PUR, allantoin relationship: creatinine, total purine: creatinine, N mic and mic P were not influenced by the energy source of the diet with average values of 10.03 g / day, 99.56 mmol / day, 4.01 mmol / day, 103.57 mmol / day, 1.57, 1.54, 58,21g / day and 363.81 g / day, respectively. Were determined following blood parameters: Gamma-glutamyl transferase (GGT), activities of the aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, total protein, alkaline phosphatase, and glucose with values of 17.4; 86.2; 22.1; 33.8; 7.0; 107.5 and 54.2 mg / dL, respectively. The blood urea values were found above the reference values (20 to 30 mg / dL), except for MGI (28.46 mg / dL). Animal fed with SCMF showed higher levels of urea in blood (P <0.05) compared with animals fed MGI diet. The blood profile of feedlot cattle was not influenced by the different energy sources of the diet, except for urea, which showed values above normal. The purine derivatives and microbial protein production were not affected by the energy source of the diet. Diets based on other energetic feeds than ground corn may be used since their costs are lower.