Dietary L-arginine supplementation enhances the reproductive performance of gilts

Arginine is a common substrate for the synthesis of nitric oxide and polyamines that are crucial for placental angiogenesis and growth in mammals. This study was conducted to test the hypothesis that dietary l-arginine supplementation may improve reproductive performance of pregnant gilts. Fifty-two pregnant gilts with body weight (BW) of 166.3 +/- 1.8 kg were housed individually in gestation crates. At d 30 of gestation, gilts were assigned randomly to corn-soybean-based diets supplemented with 1.0% L-arginine-HCl or 1.7% L-alanine (isonitrogenous control). Both diets contained 13.0 MJ metabolizable energy/kg and 12.2% crude protein and were fed to gilts at 1 kg twice daily during gestation. Backfat thickness and BW were measured and blood samples were obtained on 30, 70, 90, and 110 d of gestation. At d 110 of gestation, gilts were transferred to individual farrowing crates. The numbers of total piglets born and born alive, as well as birth weights of piglets, were recorded immediately after farrowing. Throughout the gestation, BW or backfat thickness of gilts did not differ between treatment groups. Plasma urea concentrations were lower in arginine-supplemented than in control gilts at d 90 (P < 0.010) and d 110 (P < 0.001) of gestation. Compared with the control group, arginine supplementation increased the number of pigs born alive by 22% (11.40 vs. 9.37, P = 0.032) and live litter birth weight of piglets by 24% (16.38 vs. 13.19 kg, P = 0.016). This exciting finding provides the first evidence for a marked increase of live-born piglets by 2 per litter through nutritional intervention in gilts.