Betaine and conjugated linoleic acid (CLA) may improve pig performance and increase lean mass, but the mechanisms are not well understood. Gastrointestinal tract, pancreas, spleen and mesenteric fat comprise portal-drained viscera (PDV). Nutrient and energy availability of productive tissues may be compromised by PDV because of its anatomical situation and elevated oxygen consumption. The objective of this study was to determine if the use of betaine, CLA, or both in the diet affects the net portal appearance (NPA) of proteinogenic amino acids (AA; essential and non-essential AA) in Iberian pigs. Sixteen Iberian growing barrows (19 kg body weight (BW)) were randomly assigned to one of four experimental treatments (4 pigs/treatment): basal diet (control; barley and soybean meal-based (145 g crude protein (CP)/kg dry matter (DM) and 14.7 MJ metabolizable energy (ME)/kg DM)) supplemented or not with 5 g/kg betaine, 10 g/kg CLA, or 5 g/kg betaine +10 g/kg CLA. Three catheters were placed in each pig: in carotid artery and portal vein for blood sampling, and in ileal vein for para-aminohippuric acid (PAH) infusion to measure portal plasma flow (PPF). Blood samples were taken into heparinized tubes simultaneously from carotid artery and portal vein at 0, 0.5, 1, 1.5, 2, 3 and 6 h after feeding 1200 g of diet. Blood was centrifuged, haematocrit determined, and plasma stored until PAH and AA analyses. The PPF tended to be greater (15.0%, P=0.095) for control diet compared with the other three diets. Supplementation with betaine increased NPA of essential (59%, P<0.001), and non-essential (79%, P<0.001) AA of growing Iberian pigs and, therefore, the AA availability for peripheral tissues; however, supplementation with CLA decreased (122%, P<0.001), the NPA of most essential AA.

This study was financed by grant AGL2009-08916. Ministry of Science and Innovation (Spain).