Low-Dosage Rumen Unprotected Creatine Precursor During the Transition Period in Single-Bearing Ewes Impacts Dynamic Changes in Muscle and Adipose Mass, Uterine Involution, and Fetal Programming Outcomes

Little is known about the reproductive impacts of the guanidinoacetic acid (GAA), creatine precursor, in ruminants. This study aimed to evaluate the effects of GAA supply during the transition period in ewes with single pregnancies on their reproductive response. Sixteen ewes with single pregnancy were allocated to two groups: one receiving a basal diet (n = 8) and another receiving a basal diet supplemented daily with 0.6 g/kg DM diet of GAA (RUGAA, n = 8) from 100 days of gestation to 35 days postpartum (PP). The RUGAA group showed increased feed intake after delivery and modified diet selectivity. At parturition, a smaller cotyledonary surface area and lower offspring weight at birth was observed. During PP, RUGAA exhibit a slight reduction of the loin depth and backfat thickness, and higher peripheral glutathione peroxidase level. Also in PP, RUGAA expressed a greater rate of uterine lumen shrinkage, more efficient mammary parenchyma growth and a higher relative lambs growth rate. We conclude that, supplementation with 0.6 g of GAA in single-bearing ewes improved postpartum reproductive responses, but also that, further studies are needed to efficiently align creatine demand with the distinct physiological events occurring during pregnancy and the postpartum period.