Young Scholar Presentation: The Impact of Nutrition and Reproductive Stage on Maternal and Fetal Pancreatic Exocrine and Endocrine Function in Ruminants

The ruminant pancreas plays an essential role in digestion and metabolism, however, despite its extensive exocrine and endocrine functions, relatively little is known about how it is impacted by nutrition and physiological state. As feed quality and availability vary throughout the year, an increased likelihood for reduced nutrient intake develops. The secretion of pancreatic digestive enzymes and insulin have been closely linked to dietary intake and alterations in maternal nutrient supply could result in modifications of the uterine environment and consequently fetal development. In order to evaluate the impact of various nutritional insults and dietary strategies on maternal and fetal pancreatic function, three experiments were conducted. The first of these explored various phases of the reproductive cycle and the impact of arginine infusion amid differing levels of feed intake. The second, examined the influence of nutrient restriction and melatonin supplementation on maternal and fetal pancreatic development while the third determined the effectiveness of realimentation during advancing stages of gestation. Not surprisingly, nutrient restriction caused reduced BW, pancreatic mass and pancreatic enzyme activity in maternal tissues in all experiments. In experiment 1 the infusion of arginine was unable to alter pancreatic exocrine or endocrine function during the various phases of the luteal stage. In experiment 2, the addition of dietary melatonin seemingly diminished the impact of nutrient restriction on maternal pancreatic mass and α-amylase activity while decreasing the secretion of insulin and reducing the size of insulin-containing cell clusters. Although fetal pancreatic enzymes were unaffected by treatment, pancreatic morphology exhibited greater cluster size when carried by adequately fed dams. Implementing realimentation strategies during different stages of gestation proved to act as a rescue mechanism causing a decrease in the impact of reduced feed intake and, in some cases, allowing for compensatory gain of the exocrine pancreas although the endocrine pancreas was unaffected in both maternal and fetal tissue. Interestingly, dams had greater changes in exocrine secretions while fetuses differed mainly in endocrine function as a result of poor nutritional status. Additionally, comparison of pancreatic tissue revealed a greater quantity, along with larger sizes, of insulin-containing cell clusters in fetuses than dams which appear to separate as the animal matures. Pancreatic function is controlled by many complex mechanisms and determining how these processes are regulated will provide opportunities for the beneficial manipulation of production in ruminants.