Effects of lactation on fetal survival and development in rabbit does mated shortly after parturition1

Primiparous rabbit does were mated within 12 h after parturition (d 0). They were immediately weaned (Group W; n = 31) or allowed to suckle 10 young rabbits (Group L; n = 32). Blood samples were collected at d 0, 7, 17, and 28. Feed intake and live weight were measured weekly and pregnant does (Group W, n = 24; Group L = 25) were slaughtered at d 28. Feed intake was 78% higher in L than in W females throughout gestation (P < .001). However, L females lost weight during the second half of gestation (-243 +/- 25 g) compared with W females, which gained weight (246 +/- 20 g). The weights of carcass, skin, and adipose tissues were severely reduced at d 28 in the L group (P < .01). Ovulation rate (11.0 +/- .3 corpora lutea) and early embryonic mortality (< d 15) were similar in both groups (12.3 +/- 2%), whereas late embryonic mortality (> or = d 15) was higher in L than in W does (13.9 +/- 3 vs 3.9 +/- 1%; P < .01). Fetal weight was reduced by nearly 20% in L compared with W females (P < .01). Plasma concentrations of progesterone were lower in L than in W females at d 7 and 17 (P < .001), whereas concentrations of estradiol were similar in both groups throughout gestation. These results indicate that fetal survival and development can be impaired in lactating females.