Perfil metabólico e características de carcaça e carne de bovinos nelore confinados

Abstract

The objective of this work was to evaluate finishing diets with different levels of concentrate for confined Nellore cattle, regarding the effects on the characteristics of carcass and meat produced by them and their metabolic profile, as well as the effect of blood collection period (in vivo or during exsanguination) in these parameters. For the execution of this experiment, 25 uncastrated males weighing 380.2 ± 28.7 kg were used. The experimental design was a completely randomized design, with five treatments, five repetitions and two blood sampling periods, in a split-plot scheme. During 112 dasys, the animals received diets containing 17, 34, 51 and 68% of concentrate, plus a maintenance diet with 40% of concentrate and 60% roughage restricted to 1.2% of their live weight. For blood metabolites analysis, blood samples were drawn on the 110th four hours after the morning feeding time, and on the 112th day, during slaughter. Additionally, the data were submitted to analysis of variance using the Tukey test at 5% to compare the means. Differing diets and/or blood samples studied resulted in changes in blood values of all evaluated metabolites, except for urea, blood urea nitrogen and globulin. In addition, the serum levels of cholesterol, triglycerides and globulin exceeded the maximum limit recommended by the literature in both pre-slaughter and during exsanguination collections. It was also observed that the stress experienced by the animals during their transportation and during the slaughter process affected their homeostasis. This resulted in dehydrated animals with altered energy metabolism in response to physiological changes. These changes can be evidenced by the increase in the concentrations of creatinine, uric acid, triglycerides, aspartate aminotransferase, gamma-glutamyl transferase, and glucose. Thus, it can be deduced that the plasma glucose concentration can be used as a physiological indicator of stress in Nellore cattle. For the evaluation of carcass and meat characteristics, the maintenance group was not considered, so 20 uncastrated males weighing 397.80 ± 31.31 kg were used. They were distributed in a completely randomized design, and received diets containing 17, 34, 51 and 68% of concentrate. The design was completely randomized and the results obtained were submitted to analysis of variance and regression, as well as Pearson’s correlation with the GLM and REG procedure of SAS (2004). Additionaly, carcass and meat characteristics were correlated to the studied metabolites through Pearson’s correlation test, using the CORR procedure of SAS (2004). The dry matter intake was similar between levels, however, the average slaughter weight, warm carcass and cold carcass weights had a linear increasing behavior. The cold carcass yield was positively linear. The levels of concentrate in the diets did not influence the morphometric and qualitative characteristics of the carcasses evaluated, except for the subcutaneous fat thickness, which presented a linear increase. The weights of commercial meat cuts increased linearly, however the meat of animals that received more concentrate showed less cooking losses. Increasing levels of concentrate in the diet of confined Nellore steers positively influence carcass and meat quality characteristics as well as cold carcass yields and also major meat cuts yields. Metabolites indicators of nutritional status correlate with carcass and meat parameters of cattle finished in feedlot. Plasma glucose concentration correlates positively with carcass weight and yield and can be used as an indicator of these parameters for confined Nellore cattle.