Permanent effects of starch and fiber supplid during uterine and postnatal life on first lactation performance of dairy sheep

This Thesis shows the lactation performances of sheep exposed to different dietary carbohydrates during uterine life, growing and mid lactation.The first Chapter is a literature overview of dietary carbohydrates, nutrient partitioning in lactating sheep, physiological mechanisms of insulin resistance and basis of fetal programming.The experimental hypothesis: early exposure to dietary starch or fiber might induce permanent changes of glucose metabolism increasing lactation persistency of first lactating sheep.The second Chapter described the experimental design.The third Chapter presented the lactation performances of primiparous sheep fed different carbohydrates (starch and fiber) in mid lactation. Dietary treatments did not significantly affect sheep performance.The fourth Chapter described effects of starch and fiber supplied during: 1) uterine life, 2) growing and 3) mid lactation on sheep lactation performances. Results showed that sheep exposed to starch early in life, fed fiber diets in mid lactation, had higher lactation persistency. This effect was statistically significant only for a small group of sheep in homogenous physiological status.The fifth Chapter showed results of glucose and insulin tolerance tests performed in pregnancy and lactation. Observed patterns indicated that early in life exposure to starch might induce higher insulin resistance whereas exposure to fiber might induce higher insulin sensitivity. Finally, general conclusions close the dissertation.