Grão de soja em substituição ao núcleo peletizado na terminação de novilhas Nelore em semiconfinamento ou confinamento

Abstract

The aim of this study was to evaluate the replacement of pelleted protein mix by whole soybean in high-grain diets on intake, digestibility, performance, economic evaluation, carcass and meat characteristics and ingestive behavior of Nellore heifers finished on pasture or feedlot. Twenty-four heifers aged between 16 and 18 months and initial mean live weight of 294kg ±13.51 were used, distributed in a completely randomized design, 2x2 factorial arrangement, with six replications per treatment. Four treatments, two finishing systems (high-grain on pasture and feedlot) and two protein sources in the diets (pelleted protein mix and whole soybean) were evaluated. The total period of the experiment lasted 98 days, divided into an adaptation phase of 14 days and an evaluation phase of 84 days. . In the adaptation phase, the feedlot animals had higher dry matter intake (P<0.05), while in the evaluation phase the heifers in high-grain pasture finishing had higher intakes of dry matter and nutrients (P<0.05). The pelleted protein mix diet increased the dry matter and nutrients intake, except of ether extract. In the total period, dry matter intake was higher in the pelleted protein mix diet (P<0.05). The pasture finishing system provided greater performance in the adaptation phase and total period. Better feed efficiency was observed for fed soybean heifers compared to pelleted protein mix and for feedlot heifers compared to pasture in the evaluation phase. The feedlot animals showed more time consuming concentrate, in idleness and in other activities, and in pasture, more time ruminating. The use of soybeans in high-grain diets for heifers reduces dry matter intake, but maintains energy intakes and improves feed efficiency in the evaluation phase and does not change feeding behavior, maintaining carcass characteristics and quality of the meat. Pasture finishing with high-grain diet is an interesting finishing alternative for Nellore heifers compared to the feedlot system, once it allows higher average daily gain and hot carcass weight, and similar meat and carcass traits.