Desempenho produtivo de bovinos nelore confinados

Abstract

Aimed to evaluate the effect of increasing levels of concentrate in diet of non-castrated Nelore cattle, on intake, digestibility, body weight gain, feed conversion efficiency and economic aspects. Twenty cattle were used, they were distributed in a completely randomized design of four treatments according to concentrate levels in the diet: 17; 34; 51 and 68%. The experimental period was 112 days and at the end the animals were slaughtered. The diet of 17% of concentrate was formulated to meet daily average weight gain of 1.0 kg. Measurement of body weight was carried on the first and last day of the experimental period, with the cattle under fasting. Samples of the feed offered and the leftovers were collected weekly for chemical analysis. Digestibility trial was carried out during the period between 98° and 102° of the experiment, where fecal production was estimated by the indigestible acid detergent fiber. ANOVA and regression analysis were performed in function of the concentrate levels. The financial analysis was evaluated using the gross margin of the feedlot. The intakes of dry matter (DM), crude protein (CP), non-fiber carbohydrates (NFC) and total digestible nutrients (TDN) were influenced linearly and positively (P<0.05) by increasing levels of concentrate in the diet, while intake of neutral detergent fiber (NDF) decrease. Digestibility, except for NDF, weight gain and feed efficiency were affected linearly and positively by increasing of concentrate levels in diets (P<0.05). Digestibility of CP had a quadratic effect with minimum point of 65.3% digestibility at the level of 47.7% of concentrate; while feed conversion reduced linearly (P<0.05). Weight gain and carcass yield were increased due to the increments of the concentrate level in the diets (P<0.05). Diets with concentrate level of 68% had higher production costs, although it showed highest gross margin. On the other hand, diets with 17% concentrate showed lower gross margin with negative income. Concentrate inclusion in diets of Nelore feedlot improves animal performance and nutrient digestibility. The concentrate level of 68% for Nelore cattle under the conditions of this trial promoted better productive efficiency and gross margin of the feedlot.