Reducing crude protein content with supplementation of synthetic lysine and threonine in barley - rapeseed meal - pea diets for growing pigs

Abstract

This study was conducted to determine the possibility to use synthetic amino acids to lower the nitrogen output from pig production. A performance experiment was carried out with 120triplet-fed growing pigs whose dietary crude protein was reduced from 179 g/feed unit (FU= 0.7 kg starch equivalent) to 160, 140 and 122 g/FU, respectively. The diets were supplemented with synthetic lysine and threonine to keep the level of these amino acids constant. Dietary protein reduction did not affect the growth performance or feed conversion ratio of the pigs, but it did linearly increase the portion of fat to lean in the carcass. Significant linear effect was found in back fat (p<0.001) and side fat thickness (p<0.01) and in the proportion of lean in valuable cuts and in whole carcass (p<0.05). However, the change in carcass composition was negligible down to a crude protein level of 140 g/FU. It may, therefore, be concluded that the crude protein content of the diet can be reduced by up to 20% by balancing the dietary protein with synthetic lysine and threonine.