PLASMA AMINO-ACID-UPTAKE BY THE MAMMARY-GLAND OF THE LACTATING SOW

The objectives of this study were to measure arteriovenous concentrati on (A-V) differences and estimate uptake of amino acids across the mam mary 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 ve in and the carotid artery around d 7 of lactation. Arteriovenous sampl es 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. S amples were taken at 20-min intervals for the next two consecutive hou rs. Milk production measurements and milk samples were obtained betwee n d 11 and 19. Liters of plasma to liters of milk ratio (conversion co efficient) 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 m ilk and 4,275 +/- 386 L of plasma, respectively. The A-V differences a nd the plasma flow were used to quantify daily amino acid uptake by th e mammary gland. Uptake estimates (grams/day) were 36.51 +/- 4.05 (leu cine), 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), 1 5.46 +/- 1.58 (phenylalanine), 7.61 +/- 1.12 (histidine), and 6.54 +/- 2.01 (methionine). The uptakes of arginine, leucine, isoleucine, vali ne, phenylalanine, and threonine significantly exceeded output of thes e aminoacids in the milk. These results indicate that the sow mammary gland retains specific amino acids above requirements for milk protein synthesis.