When working with multi-catheterized animals, success and failure are separated by surgical procedures and minor details in catheter design and care. The current paper is a detailed description of novel approaches to multicatheterization of pigs for investigations into nutrient absorption and metabolism of portal-drained viscera (PDV) in a native obese (Iberian) and a modern (Landrace) breed. Three Iberian and three Landrace gilts (25 kg average body weight; BW) were fitted with catheters in the carotid artery (CA), the portal vein (PV) and the ileal vein (IV). Tygon rings were attached to the catheter to mark the extent of introduction into the vessel and facilitate its fixing by means of a non-absorbable suture. The PV was catheterized through the visceral side of the left-lateral lobe of the liver and IV through a branch of the vein. The CA was secured directly in place with a purse-string suture where the artery was not occluded. Patency of the catheters was checked weekly and catheters filled with sterile heparinized saline and closed by two knots. Portal blood flow was determined to test the procedures. A 15 ml pulse dose of para-aminohippuric acid (PAH; 2% w/v) was infused into IV 45 min prior to blood sampling, followed by continuous infusion of 0·8 ml/min. Blood samples (4·5 ml) were taken simultaneously from CA and PV, using heparinized tubes, 5 min before feeding 0·25 of the total daily ration (barley-soybean meal diet; 160 g crude protein (CP)/kg; 14-14·5 MJ metabolizable energy (ME)/kg dry matter (DM); 2·4 × ME for maintenance), and every 30 min for 4 h and then hourly until 6 h after feeding. Blood was centrifuged and plasma harvested and stored at −20°C until PAH analysis. Whole-blood flow was based on the Fick principle. Post-prandial PDV blood flow was lower for the Iberian pigs than Landrace (866 and 1464 ml/min, respectively). The concurrence of access to the PV through the liver with a minimal wound, the non-occluded blood flow in CA, and the catheter design and care were all critical for the fast recovery of pigs and catheter patency. The procedures followed are recommended for studies of absorption of nutrients from the gastrointestinal tract and the impact of PDV on the metabolism of conscious, unrestrained, growing pigs.

To determine possible mechanisms of action that might explain the nutrient partitioning effect of betaine and conjugated linoleic acid (CLA) in Iberian pigs and to address potential adverse effects, twenty gilts were restrictively fed from 20 to 50 kg BW Control, 0.5% betaine, 1% CLA or 0.5% betaine 1 1% CLA diets. Serum hormones and metabolites profile were determined at 30 kg BW and an oral glucose test was performed before slaughter. Pigs were slaughtered at 50 kg BW and livers were obtained for chemical and histological analysis. Decreased serum urea in pigs fed betaine and betaine 1 CLA diets (11%; P 5 0.0001) indicated a more efficient N utilization. The increase in serum triacylglycerol (58% and 28%, respectively; P 5 0.0098) indicated that CLA and betaine 1 CLA could have reduced adipose tissue triacylglycerol synthesis from preformed fatty acids. Serum glucose, lowdensity lipoprotein (LDL) cholesterol and non-esterified fatty acids were unaffected. CLA and betaine 1 CLA altered serum lipids profile, although liver of pigs fed CLA diet presented no histopathological changes and triglyceride content was not different from Control pigs. Compared with controls, serum growth hormone decreased (20% to 23%; P 5 0.0209) for all treatments. Although serum insulin increased in CLA, and especially in betaine 1 CLA pigs (28% and 83%; P 5 0.0001), indices of insulin resistance were unaffected. In conclusion, CLA, and especially betaine 1 CLA, induced changes in biochemical parameters and hormones that may partially explain a nutrient partitioning effect in young pigs. Nevertheless, they exhibited weak, although detrimental, effects on blood lipids. Moreover, although livers were chemically and histologically normal, pigs fed CLA diet challenged with a glucose load had higher serum glucose than controls.

Para-aminohippuric acid (pAH) is a marker frequently used to measure plasma or blood flow. In sheep studies, it is recognized that its determination must include a deacetylation step to counteract the hepatic acetylation of pAH. Such a procedure is not of common usage in cattle studies although a recent suggestion of hepatic pAH acetylation in dairy cows may have important consequences for hepatic nutrient fluxes. The aims of this study were to evaluate pAH analytical methods according to international procedures of metrology and confirm hepatic acetylation of pAH in dairy cows. The effect of the matrix used to prepare the standard curve was tested, and the influence of the pAH analytical method on blood flows and subsequent net hepatic fluxes of nutrients was determined. For the first objective, accuracy profiles were established and bias, indicators of precision, and limits of quantification were reported for 2 analytical methods (without and with a pAH deacetylation step) using 2 different standard matrices (water and plasma). Second, the net hepatic flux of different nutrients was determined including or not the deacetylation step and preparing the standard curves in plasma using samples collected from 5 multicatheterized lactating Jersey cows. The choice of the matrix had a significant impact on plasma pAH concentrations as illustrated by accuracy profiles. Water matrix decreased (P < 0.01) the slope, y-intercept, and the absorbance at concentration 0 mg pAH/L of the standard curve in both methods (without and with the deacetylation), supporting that standards prepared in water should not be used to analyze plasma samples. Samples collected on cows confirmed hepatic acetylation of pAH across the liver. Deacetylation, performed using plasma as the standard matrix, increased (P < 0.05) plasma pAH concentrations from 18.4, 26, and 23.5 to 21.4, 28.9, and 27.3 mg/L in the artery, portal vein, and hepatic vein, respectively. Deacetylation decreased the hepatic venous and arterial plasma and blood flows (P< 0.05) by 9 and 55%, respectively, modifying the net hepatic flux of acetate, total amino acid, and oxygen by more than 19% (P < 0.05). In conclusion, our results highlight the importance of including a deacetylation step in the pAH analysis method in cattle studies and of using plasma as standard matrix.

Compared to modern breeds, Iberian pigs have lower rates of muscle protein deposition and greater viscera weight. Factors that limit growth performance of Iberian pigs are unknown. We hypothesized that differences in net portal appearance of the essential AA Lys and Met might partially explain the lower growth rate reported in Iberian pigs compared to modern breeds. Net portal appearance of AA was measured in 6 Iberian and 6 Landrace gilts (28 kg BW) fitted with chronic catheters in the portal vein, carotid artery, and mesenteric vein. Blood samples were taken for 6 h after feeding 2 isoenergetic diets (14.0 to 14.5 MJ ME/kg DM) with low CP (LCP) and high CP (HCP) (13 vs. 16%, respectively) in a crossover design after a 1-wk adaptation. Net portal appearance of Lys was greater (P < 0.05) when pigs consumed the HCP than LCP diet (23 vs. 15 μmol/min); breeds did not differ. Net portal appearance of Met tended to be higher (P = 0.076) for pigs fed HCP than LCP diet (4.4 vs. 3.6 μmol/min); breeds did not differ. In conclusion, differences in portal appearance of Lys and Met did not exist between Iberian and Landrace pigs fed barley (Hordeum vulgare)-soybean (Glycine max) diets with low and high protein concentration.