Impact of arginine supplementation on serum prolactin and mRNA abundance of amino acid transporter genes in mammary tissue of lactating sows

Uffe Krogh, Chantal Farmer, Lee-Anne Huber, Peter K Theil, Nathalie L Trottier

This study was conducted to test the hypothesis that supplemental dietary Arg to late-pregnant and lactating sows increases serum prolactin concentrations and mRNA abundance of SLC7A1, SLC7A2 and SLC6A14 in mammary parenchymal tissue. From d 108 of gestation and until d 21 of lactation, sows were fed a diet either supplemented with 0.10 g of L-Arg/kg body weight (BW) per day (n = 10, ARG) or 0.34 g of L-Glu/kg BW per day (n = 10, control). Litters were standardized to 10 piglets on d 1 of lactation and piglets were weighed on d 1, 7, 14 and 21 of lactation. Sow BW was recorded on d 108 of gestation and d 1, 10 and 21 of lactation. Lactation sow feed intake was recorded daily. Mammary parenchymal tissue was biopsied on d 5 of lactation to measure mRNA abundance SLC7A1, SLC7A2 and SLC6A14. On d 4 and 18 of lactation, blood samples were collected from sows at 2, 4 and 6 h post-feeding to measure serum prolactin concentrations. Milk samples were collected on d 4, 10 and 18 of lactation to measure fat, lactose, urea N, and true protein concentrations. Sow BW, backfat and feed intake over all sampling days did not differ between treatments. Piglet BW on d 1 and mean BW during lactation tended to be greater for the ARG treatment than the control treatment (P = 0.12 and P = 0.15, respectively). Sow milk yield and composition (fat, protein, lactose and urea N) and mammary mRNA abundance of candidate genes did not differ between the ARG and the control group. Compared to controls, serum prolactin concentrations tended to be greater (P = 0.08) in ARG sows on d 4 of lactation, and did not differ on d 18. Current findings show a potential beneficial effect of dietary supplementation with Arg to late-pregnant multiparous sows on BW of their piglets on d 1. Dietary Arg supplementation at a rate of 0.10 g/kg BW during late pregnancy and lactation tended to increase serum prolactin concentrations with no increase in mammary transcript abundance of SLC7A1, SLC7A2 and SLC6A14 in early lactation.