Desempenho produtivo e características de carcaça e da carne de novilhas e vacas alimentadas com dietas contendo milho inteiro ou moído

Abstract

This study aimed to evaluate the effect of corn processing, whole or ground-corn diets, on feed intake, performance, blood biochemical profile, finishing costs, carcass traits and meat quality of heifers and cows during the dry season. Data were analyzed as 2X2 factorial arrangement (two animal categories: cows and heifers; and two corn types: whole and ground corn) in a completely randomized design, with four treatments and eleven replicates per treatment. Twenty-two Nellore heifers with an initial body weight of 256.9 kg and 18 months of age, and 22 adult crossbred cows with an initial body weight of 326.8 kg were used. The experimental period lasted 84 days for cows and 78 days for heifers. Cows had higher (P<0.05) initial and final body weight. Total cholesterol concentrations were higher (P<0.05) for heifers. Cows had higher serum total protein and urea concentrations (P<0.05). Cows showed higher (P<0.05) acquisition cost per head, gross revenue, feed cost per kg of live weight gain, lower net revenue and profitability. Cows had a higher cost per kg of live weight gain (P<0.05), and lower net revenue, regardless of the ratio arroba:corn sack price (60 kg). Cows showed higher gross revenue (P<0.05), and lower net revenue, regardless of the arroba price at the time of sale, except for net revenue (P>0.05) when the sale price of the arroba was R$ 135.00. Cows had higher (P<0.05) carcass weight (hot, standard, cold) and fat trim weight. Heifers had higher (P<0.05) backfat thickness. Animals fed ground corn-diets had higher (P<0.05) area of the Longissimus lumborum muscle. Relative to the beef color, cows had higher values (P<0.05) for redness, yellowness, and chroma, in addition to the lower shear force. The crude protein content of the meat was influenced (P<0.05) by the animal category, with higher values for heifers. Corn grain processing does not alter blood parameters, feed intake and performance of grass-fed animals supplemented with high-concentrate. The animal category influenced the serum concentrations of cholesterol, total proteins, and urea, indicating an influence of the diet and age on these parameters. Finishing heifers and cows is a feasible strategy, and there is no difference between corn processing types in economic terms. However, finishing heifers is more recommended due to the higher net revenue and profitability, although these results are dependent on the price of the inputs and the acquisition cost per arroba. Corn grain processing does not alter the quantitative carcass traits, meat chemical composition and meat quality from heifers and cows, except for the area of the Longissimus lumborum muscle, which was higher for animals fed ground corn. Finishing heifers and cows under grazing conditions with high-concentrate during the dry season results in similar carcass yields for both animal categories. Heifers had lower fat trim weight in carcass than cows and a higher backfat thickness. Under the conditions of the present study, the meat from cows was more tender and redder than the meat from heifers.