Influence of progesterone supplementation on foetal survival in concurrently pregnant and lactating does

An experiment was conducted to assess the influence of progesterone levels on late foetal mortality (second half of gestation) in concurrently pregnant and lactating does. All the females were mated within 12 h of parturition (d 0), and slaughtered on d 28 to study reproductive performance and body composition. Females were allowed to lactate 10 young and received either 2 progesterone implants (group P, n = 29) or 2 empty implants (group C, n = 29) on d 7. The feed intake, the live-weight variations of females during gestation, the growth of suckling litters, as well as the foetal weight and body composition of the does at slaughter, were similar in both groups. The concentration of progesterone was higher in group P than in C on d 16 and 25 (P < 0.01). The ovulation rate and late foetal mortality were similar in both groups but the early mortality was lower (12.3 vs 21.2%; P < 0.05) and the total number of foetuses on d 28 (live + resorbed + dead) was higher (9.8 vs 8.7; P < 0.05) in group P. These results indicate that progesterone supplementation improves early foetal survival but cannot increase late foetal survival in concurrently pregnant and lactating does.