This experiment aimed at evaluating the influence of the reduction of gross protein (GP) and the supplementation of synthetic amino acids on the performance of castrated male swines kept in an environment of thermoneutrality (24 °C). Eighty cross-bred piglets (Landrace x Large White) were used, with an initial average weight of 9 kg and an average age of 23 days. The animals were distributed in a randomized design, of five treatments (18, 17, 16, 15 and 14% GP), eight repetitions and two animals in each experimental area. The experimental feed was supplied ad libitum until the end of the experiment, when the animals reached 23 kg average weight (63 days). The temperature and average relative humidity inside the shed were 24 °C and 78.7%, respectively. The Globe Temperature and Humidity Index calculated for the period was 70.4. No significant effect of the reduction of the gross protein level in the feed was observed on the performance variables (feed consumption, weight gained and dietary conversion). The treatments exhibited an effect on the absolute and relative stomach weight and on the absolute intestine weight, where the highest values were observed for the animals that received the feed with the highest gross protein levels. It was concluded that the GP level of the feed can be reduced from 18 to 14%, without harm to the performance of male swine from 9 to 23 kg kept in an environment of thermoneutrality, as long as adequately supplemented with limiting essential amino acids.
thermoneutral environment; amino acids; swine performance; animal nutrition
