Plasma amino acid uptake by the mammary gland of the lactating sow.

The objectives of this study were to measure arteriovenous concentration (A-V) differences and estimate uptake of amino acids across the mammary gland in lactating sows. Four sows were used in Trial 1 and nine sows in Trial 2. Cannulas were fitted in the right anterior mammary vein and the carotid artery around d 7 of lactation. Arteriovenous samples were obtained on d 11, 14, 17, and 20. Litters were separated from the sows for 90 min, after which the first blood samples were drawn. Samples were taken at 20-min intervals for the next two consecutive hours. Milk production measurements and milk samples were obtained between d 11 and 19. Liters of plasma to liters of milk ratio (conversion coefficient) was estimated with the Fick method using A-V difference for lysine and milk lysine concentration. The conversion coefficient and the daily plasma flow were 541.41 +/- 35.72 L of plasma per liter of milk and 4,275 +/- 386 L of plasma, respectively. The A-V differences and the plasma flow were used to quantify daily amino acid uptake by the mammary gland. Uptake estimates (grams/day) were 36.51 +/- 4.05 (leucine), 31.24 +/- 3.64 (arginine), 23.39 +/- 2.97 (lysine), 21.22 +/- 1.96 (valine), 18.36 +/- 1.92 (isoleucine), 15.9 +/- 1.9 (threonine), 15.46 +/- 1.58 (phenylalanine), 7.61 +/- 1.12 (histidine), and 6.54 +/- 2.01 (methionine). The uptakes of arginine, leucine, isoleucine, valine, phenylalanine, and threonine significantly exceeded output of these amino acids in the milk. These results indicate that the sow mammary gland retains specific amino acids above requirements for milk protein synthesis.