Efficiency of threonine utilization in the growing pigs

Objective. This study aimed to determine the marginal efficiency of threonine utilization in growing pigs by using the nitrogen balance technique. Materials and methods. Twelve castrated pigs with an average live weight of 72±2 kg were housed in metabolic cages maintained in a temperature controlled room of 22±3°C. The treatments consisted of four diets calculated to meet 30, 45, 60 and 70% of the nutritional requirements of standardized ileal digestible threonine. The amino acids others than threonine were maintained at least 15% above threonine requirements, expressed in terms of ideal levels. The amount of feed supplied was calculate to provide 2.6 times the metabolizable energy requirements for maintenance and adjusted daily according to an expected daily gain rate of 0.8 kg. Results. Pigs consumed 1.65 g kg-1 BW0.75 nitrogen daily, on average and 61% was retained and, as a result, 39% was excreted, being 31% through the feces and the remainder (69%) in the urine. The pigs showed a linear retention of threonine in response to the increase of standardized threonine intake. For each gram of standardized threonine intake 0.37 g were lost during the metabolism. Conclusions. It is concluded that for calculating nutritional requirements of standardized threonine of pigs by the factorial method, it is possible to use the utilization marginal efficiency of 0.63.