Dietary supplementation with N-carbamylglycinate (CGly) improved feed source proline absorption and reproductive performance in sows

Nutrient requirements are increased in the late-gestation period due to the faster growth of the foetal-placental unit and maternal erythrocyte mass. Glycine, proline and arginine are important amino acids that could improve foetal growth and development. The present study aims to investigate the effects of a derivative of glycine (N-carbamylglycinate, CGly) on the amino acid profiles and reproductive performances of late gestation sows. Thirty-two multiparous gestating sows (∼d 80) were selected, and randomly assigned into two groups: (1) control and (2) treatment (CGly, 800 mg kg-1) from day 85 of gestation to parturition. The serum amino acid profiles at day 110 of gestation and reproductive performance were investigated. The results showed that dietary supplementation of CGly in the late gestation period significantly improved the levels of glycine (p < 0.05) and proline (p < 0.01) in the serum of the perinatal sows, and thereafter improved the litter birth weights (p < 0.05) and number born alive (p < 0.1). Based on the in vitro studies, the improvement of proline levels is probably due to the induced expression of SLC6A20 and SLC38A2. Further studies should focus on the details of amino acid absorption, especially the competitive and cooperative absorption processes for different amino acids and derivatives.