Consequences of different patterns of feed intake duping the estrous cyclein gills on subsequent fertility

The impact of different patterns of feed restriction between d 1 and 15 of the estrous cycle on subsequent reproductive performance of 23 trios of lit termate gilts was tested. Some gilts were fed a high plane of nutrition (HH gilts) throughout the cycle, in contrast to HR gilts, which were restricte d from d 8 to 15, and RH gilts, which were restricted from d 1 to 7. During feed restriction, weight gain in RH gilts (2.5 +/- .7 kg) was lower (P = . 006) between d 1 and d 7 than in their HH and HR littermates (5.6 +/- .7 an d 5.6 +/- .8 kg, respectively) and it was lower (P = .0001) in HR gilts (5. 5 +/- .5 kg) between d 8 to d 15 than in their HH and RH counterparts (8.5 +/- .4 and 9.4 +/- .5 kg, respectively). There were no differences in backf at changes among groups. Embryonic survival in HR gilts at d 28 of gestatio n (68.3 +/- 4.8%) was lower (P < .05) than in HH and RH gilts (83.6 +/- 4.3 and 81.7 +/- 4.5%, respectively). Plasma progesterone concentrations in HR gilts were lower (P < .05) at 48 and 72 h after onset of standing estrus ( .82 +/- .2 and 3.6 +/- .5 ng/mL, respectively) than in HH and RH gilts (1.4 4 +/- .2 and 1.24 +/- .2 ng/mL, 5.0 +/- .4 and 5.0 +/- .5 ng/mL, respective ly at 48 and 72 h). No differences in ovulation rate were observed among tr eatments. Placental area was positively correlated to embryo size at d 28 ( embryo size = .0003 x (area) + 18.35; r = .28, P = .03) but placental volum e was negatively correlated to the number of embryos in utero (placental vo lume = -4.317 x (number) + 207.55, r = .39, P = .002). These data demonstra te that the timing of feed restriction during follicular development has im portant consequences for subsequent embryo survival, possibly mediated by d ifferences in progesterone concentrations in early pregnancy.