- Volume 26 Issue 9
This study was designed to describe the effect of the protein quality at different intake level of protein on the protein metabolism in the whole body of growing pigs with a simulation model. Varying to the protein level in feeds, four simulations were conducted. The feed protein level, represented as proportions of digestible protein to the metabolic energy (DP/ME, g/MJ), were 6-8, 11-13, 17-19, and 23-25 DP/ME, respectively. Two protein quality and six weeks of growth time were used at each simulation. The objective function for the simulations was protein deposition in the whole body, which was calculated from the experimental results. The parameters in the simulation were determined by the parameter estimation technique. The results obtained from the simulation were as follows: The protein synthesis and breakdown rates(g/day) in the whole body was increased with the increase of protein quality only at lower or required level of protein intake. They showed a parallel behavior in the course of growth, irrespective of quality and level of feed protein intake. The simulated protein deposition and protein synthesis showed a linear relationship between them at different protein quality and level. The affinity parameter showed a linear relationship between them at different protein quality and level. The affinity parameter showed that arginine, tryptophan and isoleucine were more efficient in the stimulation ofbody protein synthesis. Lysine and phenylalanine+tyrosine were less efficient. The oxidation parameter showed that histidine, pheyalanine+tyrosine were less efficient. The oxidation parameter showed that histidine, phenyalanine+tyrosine, and methionine+cystine were oxidized in larger magnitude than lysine and threonine. The oxidation parameter of most amino acids increased with the increase of protein intake beyond the requirement level, but not any more at highest protein intake level. Finally it was found that the improvement of feed protein quality at the lower or required level of protein intake increase protein deposition through a parallel increase of protein synthesis and breakdown.