low protein, amino acids supplemented diets: performance and expression of amino acids transporters in pigs

Twenty four pigs (21.6 kg initial BW) distributed in four treatments were used to evaluate the effect of the form (free vs. intact protein) in which AA are added to diets on performance and expression of AA transporters in the small intestine. Dietary treatments were: 1, wheat + free AA (FAA); 2, as in 1 + non-essential nitrogen (NEN); 3, wheat-soybean meal (SBM) + free AA (W-SBM+FAA); 4, wheat-SBM (W-SBM). At the end of the experiment eight pigs (four FAA and 4 W-SBM) were sacrificed to collect intestinal mucosa samples. There were no differences in average daily gain, feed intake and feed conversion between dietary treatments (P>0.10). In duodenum, expression of b0,+ was higher in pigs fed the W-SBM diet (P=0.036). In ileum, y+L expression tended to be higher in pigs with the FAA diet (P=0.098). Expression of all transporters was higher in jejunum than in duodenum or ileum. These results indicate that FAA can substitute up to eight percentage units of protein in W-SBM diets without affecting pig performance; NEN does not seem to be limiting in very low protein diets for growing pigs. Also, the form in which AA are included in the diet affects the expression of some AA transporters in the small intestine of pigs.