| dc.description.abstract | Arginine and its metabolites are essential for optimal growth and development as well as reproductive efficiency, with a specific interest to improve placental development and fetal survival. Currently classified as a conditionally essential amino acid, little information exists about arginine synthesis in the horse and thus dietary requirements specific to the horse. Therefore, a series of studies were conducted to test the hypothesis that horses of different age groups can utilize glutamine and proline for the de novo synthesis of citrulline and arginine using jejunal enterocytes from horses of three different age groups as well as the dietary supplementation of arginine (50 mg/kg BW/d) can be used as a potential strategy to enhance placental vascularity and nutrient transport throughout gestation in aged mares. The initial study demonstrated that incubated equine enterocytes were able to utilize glutamine as a major metabolic fuel, similar to the pig and sheep, (in vitro) except equine enterocytes did not oxidize proline, possibly due to the absence or limited enzyme activity. Furthermore, regardless of age, equine enterocytes synthesized ornithine from glutamine and proline, but failed to convert ornithine into citrulline and arginine. Further studies were conducted in aged pregnant mares to determine the effects of arginine supplementation (50 mg/kg BW/d) on mare performance throughout gestation, placental characteristics, and the impacts on the resulting foal. Dietary supplementation of arginine increased mobilization of adipose tissue throughout pregnancy when compared to control mares, and increased blood perfusion to the uterus in pre-partum mares. At parturition, foaling and placental variables did not differ between the control and arginine-supplemented mares. This study had a small population which is a common challenge for equine studies; however, more sensitive molecular changes are valuable for use in smaller populations that may be indicative of maternal nutrition affecting the cellular and molecular mechanisms of placental function. Currently, more information is needed in order to understand arginine metabolism in the horse, regardless of age or physiological status. | |
