Evaluation of factorial methods to estimate lysine requirements for barrows and immunocastrated pigs

Abstract

The aim of this study was to compare the digestible lysine requirements of castrated and immunocastrated pigs, generated via three factorial methods based on the performance of these animals. This study was divided into two steps. In the first step, an experiment was conducted to evaluate the performance of castrated and immunocastrated pigs. In the second step, the performance data were used to evaluate the nutritional requirements generated by three factorial methods. A total of 48 pigs (24 barrows and 24 immunocastrated) from a commercial line, with an average initial body weight of 29.3 ± 1.9 kg at 75 days of age and a final body weight of 129.9 ± 9.0 kg at 177 days of age, were used. The experimental diets were formulated based on the ideal protein concept in a nutritional programme of four diets. Immunocastrated pigs had lower feed intake, greater weight gain and better feed conversion in relation to physically castrated pigs, but after the application of the second dose of the vaccine, there was an increase in feed intake. There was a difference between the factorial methods used to estimate the lysine requirement of growing and finishing pigs, especially considering lysine deposition efficiency. According to the tested methods, entire males submitted to immunocastration require a higher amount of lysine, compared with surgically castrated pigs.