Suplementação de novilhas na recria e terminação.

Abstract

This dissertation was elaborated from two experiments to evaluate the effect of increasing levels of energetic supplementation in the rainy season during the backgrounding phase on the performance, ingestive behavior and carcass characteristics of Nellore heifers grazing Panicum máximum cv. Mombasa. In both experiments the same 32 Nellore heifers were used, with initial average body weight of 192 ± 11.87 kg and 15 months of age. The experimental design was the completely randomized. The treatments consisted of four levels of supplementation: control treatment - mineral salt ad libitum, 0.5; 1.0 and 1.5% of BW in the rainy season (experiment 1) and only 1% supplementation during the transition rainy/dry season for all animals (experiment 2) . Experiment I was carried out during the rainy period from January to April 2016. The treatments during the backgrounding phase consisted of four levels of supplementation: control treatment - mineral salt ad libitum, and 0.5; 1.0 and 1.5% body weight of concentrate. As the level of supplementation increased, there was an increase (P<0.05) in average daily weight gain, total weight gain and final weight, and greater gain in body condition score. The weight gain per area, stocking rate and weight gain was higher in animals supplemented with levels 1.0 and 1.5% of BW when compared to mineral salt. Increasing supplies of concentrate did not influence (P>0.05) glucose, albumin and urea levels. However, it promoted a decrease (P<0.05) in triglyceride and total protein levels and an increase (P<0.05) in the serum creatinine level. There was a reduction (P<0.05) in grazing time and total chewing time as the level of supplementation increased. The rumination time and total chewing number was not influenced (P>0.05) by the increasing supply of concentrate. The use of energy supplementation with higher levels in the rainy period during the backgrounding phase optimizes the weight of Nellore heifers and the weight gain per area in Mombasa grass pasture, reduces grazing time, and maintains normal metabolic indicators of blood. Mombasa grass pasture in the rainy period presents potential to provide a daily average gain above 800g using only mineral salt. In Experiment II, which occurred in the rainy/dry transition period (May to July), all heifers received the same amount of concentrate, 1.0% of BW until slaughter. There was no effect (P>0.05) of the level of supplementation offered in the backgrounding phase for average daily gain and total weight gain during the finishing phase, for slaughter weight, hot and cold carcass weight, hot and cold carcass yield, subcutaneous fat thickness, carcass cooling loss, loin eye area and carcass percentages of muscle and bone. Increasing the supplementation level during backgrounding resulted in linear increase (P<0.05) in fat trimming, carcass fat percentage, pistol and side cut weights and carcass conformation. The concentrate level during backgrounding did not influence (P>0.05) the degree of marbling of meat, the forequarter weight and the metric variables of the carcass. The pH, luminosity and red and yellow indices as well as the chemical composition of the meat were also not influenced (P> 0.05) by the increased levels of supplementation offered in the backgrounding. Energetic supplementation during backgrounding of Nellore heifers for slaughter does not present an advantage, since it does not alter during finishing the performance between supplemented animals and animals receiving only mineral salt. Supplementation during backgrounding improves the carcass characteristics, but it is only feasible if there is remuneration for the additional costs of supplementation.