Undernutrition during early follicle development has irreversible effects on ovulation rate and embryos

This study assessed carry-over effects of energy level during the early antral phase and subsequent follicular phase on follicle recruitment and ovulation rate. Gilts (n≤45) were fed a standard diet to a low (L, ∼1.2kg day-1) or high (H, ∼2.7kg day-1) level during the early antral (luteal) phase, and subsequently fed a H or L feed level during the follicular phase, resulting in four treatment groups (HH, HL, LH and LL). Follicle size at the end of the luteal phase was greater for gilts fed a high feed level previously (3.3vs3.0mm; P <0.05). During the follicular phase, high feeding increased follicle size at Day 5 (6.9vs6.2mm; P<0.005) and plasma oestradiol concentration (P <0.05). Nevertheless, a low feed level during the luteal phase reduced ovulation rate (14.4vs13.2; P <0.05) and embryo number (12.6vs10.5; P <0.05), and this was not counteracted by feed level during the follicular phase. Plasma progesterone concentration after ovulation was lower for LL gilts than for other treatments (P <0.05). These results indicate that undernutrition during early antral follicle development may have a residual effect on follicle recruitment and quality. © CSIRO 2012.