Ren, Ping2017-03-142017-03-142016-11https://hdl.handle.net/11299/185134University of Minnesota Ph.D. dissertation. November 2016. Major: Animal Sciences. Advisor: Samuel Baidoo. 1 computer file (PDF); ix, 292 pages.In this dissertation, a series of experiments were conducted to determine the effects of differential feeding levels during gestation on sow and litter performance, nutrient digestibility and energy homeostasis. In Exp. 1, a total of 160 multiparous sows were allotted to 1 of 4 dietary treatments using a randomized complete block design with BW (BW) and backfat (BF) as the blocking criteria. All sows were fed one common corn-soybean meal-based diet with the amount of 1.0 × maintenance energy intake (100 × BW0.75 kcal ME/d) throughout gestation except 3 periods of 7 d when dietary treatments were imposed on d 27, d 55 and d 83 of gestation. During the 3 short periods, sows were fed 1 of 4 different feeding levels: 0.5, 1.0, 1.5 and 2.0 × maintenance energy level (0.5M, 1.0M, 1.5M and 2.0M, respectively). In Exp. 2 and 3, a total of 18 gilts were allotted to 1 of 3 dietary treatments to evaluate the effects of different feeding levels during 3 short periods of gestation on apparent total tract digestibility (ATTD) of energy and nutrients, and to assess the effects of feeding levels on hunger status and energy homeostasis. The dietary imposing periods were the same as Exp.1, with the exception that only 3 feeding levels (0.5M, 1.0M and 2.0M, respectively) were imposed during these 3 periods. Results showed that feeding gestation sows at 1.5M or 2.0M feeding levels for 3 weeks with 1.0M feeding level during the rest of gestation can achieve optimal reproductive performance. Additionally, sow BW gain efficiency, energy and nutrient digestibility were maximized at 1.0M feeding level. Furthermore, diurnal acyl ghrelin concentrations profile exhibited a flat pattern in pregnant gilts. Acyl ghrelin and NEFA were the best physiological indicators for energy homeostasis. This study provided insight to evaluate the hunger status in pregnant sows, which could be used as a reference to improve the welfare of gestation sows.enenergy homeostasisfeeding levelsgestationghrelinnutrient digestibilityreproductive performanceThesis or Dissertation