Long-term caloric restriction to ameliorate the fertility by redirection of metabolism in female rabbits

To study the effect of feeding level during rearing on body growth andsubsequent reproduction of rabbits, feed was provided either adlibitum (AL, n¼52) or gradually decreased (R, n¼52) from 6 to 12weeks of age from 100 to 58% of AL (restriction period) andthereafter steadily increased until 17 w k(recovery period) whenanimals were inseminated. Blood samples were taken weekly from 11animals per treatment. Body growth of R was reduced during therestricted period (29.0 vs 40.7 g/d for R and AL, respectively;P<0:05), but increased (38.3 vs. 24.1 g/d, respectively) in the recoveryperiod. NEFA steadily dropped in both groups, while triglycerideswere higher in R at start, but decreased (P<0:05) from 11 wkonwards, whereas they increased in AL. Glucose was constantly lower(P<0:05) in R than AL from 8 to 14 wk. Both insulin and IGF-1levels paralleled those of glucose being lower in R (P<0:05). Only inthe last 2–3 weeks the values of both groups overlapped. Leptin levelswere similar until 10 weeks and then increased in AL, but not in Ranimals. In the last week, when R animals were flushed, leptinconcentrations raised five-fold and were similar to that of AL.Although hormonal and metabolic profiles conductive to bothcarbohydrate and lipid metabolism were markedly different duringrearing, reproduction was unaffected as fertility rate (83.0vs. 80.8%),and litter size (6.5vs. 7.0) were similar in groups R and AL,respectively.