Effects of overnutrition and undernutrition on in vitro fertilization (IVF) and early embryonic development in sheep

Nutrition has been shown to influence several reproductive functions including hormone production, oocyte competence and fertilization, and early embryonic development. To determine effects of maternal diet on in vitro fertilization (IVF) and early embryonic development, ewes (n = 48; 58.4 ± 1.7 kg initial body weight [BW]; 2.3 ± 0.1 initial body condition score [BCS]) were divided into control, overfed (ad libitum feeding) and underfed (60% of control) nutritional planes for 8 weeks before oocyte collection. Ewes were individually fed once daily with pelleted diets containing 2.4 Mcal of ME/kg and 13% CP (DM basis). Control ewes were fed to maintain BW and offered 760 g/day/50 kg. Synchronization of estrus was performed using progestagen sponges for 14 days. Follicular development was induced by twice daily injections of follicle stimulating hormone (FSH) on days 13 and 14 of the estrous cycle. During the 8 week experiment, control ewes lost 1.0 ± 0.9 kg, overfed ewes gained 11.8 ± 1.1 but underfed ewes lost 14.2 ± 0.9 kg, and BCS increased by 0.7 ± 0.2 and by 2.0 ± 0.1for control and overfed ewes, respectively, but decreased by 0.7 ± 0.1 for underfed ewes to compare with initial BCS. Oocytes were collected from all visible follicles on day 15 of the estrous cycle. After IVF, the proportion of developing embryos was evaluated throughout the 8 day culture period. Overnutrition and undernutrition decreased (P < 0.0001) rates of cleavage, and morula and blastocyst formation (from 85% to 51% and 48%; from 63% to 18 and 28% and from 40% to 5% and 6% for control, overfed and underfed ewes, respectively). However, number of visible follicles (large and small), total number of oocytes, number of healthy oocytes and percentage of healthy oocytes were similar for control and underfed ewes. These data indicate that overnutrition and undernutrition of donor ewes resulting in lower BW and BCS, has a negative effect on oocyte quality which results in lower rates of cleavage, and morula and blastocyst formation. These data demonstrate that nutrition level substantially affect IVF and early embryonic development.