Net Portal Appearance of Amino Acids in Iberian and Landrace Pigs Fed Different Protein Content in the Diet

SIMPLE SUMMARY: Iberian pig (Sus mediterraneus) is a rustic breed that thrives in the Mediterranean forest in the Southwest of the Iberian Peninsula, traditionally raised in open range, grazing acorn and grass. The information on nutrient requirements of Iberian pigs compared with modern breeds is scarce and derived from modern breeds, even though there are evidences that they have distinct metabolic and nutritional features, showing a much lower growth rate and protein deposition. This study attempts to shed light on this issue. By using net portal appearance, the intestinal absorption of nutrients is considered, and therefore the nutrient availability for pig growth is estimated. The present study focused on the net portal appearance of amino acids in Iberian pigs compared to a modern breed known as Landrace. Iberian pigs showed a lower net portal appearance of amino acids than Landrace pigs, regardless of the content of protein in the diet. Differences in net portal appearance of amino acids may partially explain the lower growth rate of Iberian pigs compared to modern breeds, maybe as result of a greater use of amino acids by the gastrointestinal tract. Strategies supplementing key gut amino acids in support of gut function may improve pig performance during the productive period. ABSTRACT: Iberian pigs have low rates of muscle protein deposition compared with modern breeds. Differences in net portal appearance (NPA) of amino acids (AA) might partially explain that. NPA of AA was measured in six Iberian and six Landrace gilts (28 kg) fitted with catheters in portal and mesenteric (para-aminohippuric acid infusion) veins, and carotid artery. Blood samples from porta and artery were simultaneously taken at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, and 6-h after feeding two isoenergetic diets (14–14.5 MJ metabolizable energy/kg dry matter) with different crude protein (145 (LCP) and 187 (HCP) g/kg dry matter) content. NPA of essential AA (EAA) and non-essential AA (NEAA) was lower (p < 0.05) in Iberian than Landrace pigs, and in LCP than HCP diet. Fractional absorption (NPA/AA intake) of EAA, NEAA, and total AA was, respectively, 36, 49, and 44% lower in LCP than HCP diet in Iberian pigs; and 8, 2, and 4% greater in Landrace pigs. Fractional absorption of EAA, NEAA, and total AA was 42, 68, and 60% lower in Iberian than Landrace pigs fed LPC diet; and 1, 36, and 26% when fed the HCP diet. NPA of AA may partially explain the low growth rate of Iberian pigs.