PERFORMANCE AND CARCASS CHARACTERISTICS OF SWINE AT 50 KG FED DIETS WITH DIFFERENT ENERGY LEVELS AND REDUCED LEVELS OF CRUDE PROTEIN

The aim of this work was to evaluate the effects of different levels of metabolic energy (ME) in diets with a reduced level of crude protein (CP) on the performance and carcass characteristics of growing swine. Thirty-two high-performance barrows (initial weight of 22.5 +/- 1.43 kg and final weight of 50.81 +/- 2.54 kg) were distributed in a randomized block design with four treatments (three levels of ME - 3,060, 3,230 and 3,400 kcal/kg - in diets with 14% CP, and one control treatment with 3,230 kcal ME/kg and 18% CP) and four replicates. The diets were formulated with a true digestible basis of amino acids present in the feed, with methionine and threonine concentrations corrected as a function of lysine levels. The animals were slaughtered and their carcasses were studied. The ME levels did not affect the average weight gain, the feed: gain ratio, the backfat thickness or the loin eye area. A higher carcass yield and a higher carcass meat: fat ratio were observed in the animals that received the 3,230 and 3,060 kcal/kg ME levels. Compared to the control treatment, only the 3,400 kcal/kg ME level had a lower average daily feed intake. It is concluded that the CP level in diet should be reduced from 18% to 14% and the metabolizable energy level should be increased, thus reducing the feed intake and increasing the carcass meat: fat ratio without affecting the animal weight gain.