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.
(CNL : 39,7 g, RNL : 39,3 g ; P < 0,001) et leur poids augmente linéairement avec 8p1428 (r = 0,47; P < 0,001). Ces résultats suggèrent que l'effet défavorable de la lactation sur la mortalité et la croissance foetales peut être diminué par une réduction de la taille de la portée allaitée.lapin / lactation / mortalité frntale / croissance fcatale / rationnement
Summary ― Two experiments were conducted in order to determine the influence of nutritional deficit on foetal survival and growth in rabbits does. All females were mated within 12 h of parturition and all the young were removed at that time. In experiment 1, females were fed close to ad libitum (C1, n = 20), or restricted to 100% (M1, n = 20) or 75% (R1, n = 19) of the maintenance energy requirement. On d 28 of gestation, foetal mortality was similar in the 3 groups, whereas foetal weight and protein content of the litters were reduced in feed-restricted groups (P < 0.001 ). In experiment 2, females were fed ad libitum (C2, n = 12) or were restricted to the same level as in R1 l (R2, n = 13). Blood samples were collected on d 17 and 28 of gestation before and after (1 and 3 h) a standardized meal. Pre-and postprandial concentrations of non-esterified fatty acids and urea were lower in the R2 than in the C2 females (P < 0.01 ). Preprandial concentrations of glucose were similar in both groups at d 17, and higher in the R2 group than in the C2 group at d 28. The postprandial concentration of glucose was higher 1 h after the meal and lower 3 h after the meal in the R2 group (P < 0.01).
Summary ― 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.
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