The objective of this study was to determine the metabolizable energy (ME) requirement for starting barrow pigs. Forty-three animals, selected for their high lean gain, were allotted in a completely randomized block design, divided in four treatments with five blocks and two animals in each experimental unit. The diet in Treatment 1 consisted of 3,264 kcal of ME/kg containing 0.96% of digestible lysine, 0.55% of digestible methionine+cystine, 0.60% of digestible threonine, and 0.188% of digestible tryptophan reaching the ideal protein pattern. The diets in Treatments 2, 3, and 4 were similar to the diet in Treatment 1; nevertheless, the levels of ME in Treatments 2, 3, and 4 were 2, 4, and 6% higher than those in Treatment 1. The lysine:ME ratio, was mantained the same (2.82 g) in all treatments. The daily feed intake (DFI) and the feed:gain ratio (F:G) were not affected by the levels of ME. There was a linear increase of daily weight gain (DWG) and of daily energy intake (DEI). Later, a linear reduction in carcass protein percentage (CPP) and a linear increase of fat content and daily fat accretion (DFA) occurred. Results suggested that the required ME was of 3,264 kcal/kg or less for improved barrows (15 to 30 kg), of the dam line, fed with diets containing 0.96% of digestible lysine, formulated according to the ideal protein concept.
Synthetic amino acids; carcass; performance; plasma urea nitrogen; energy requirements
