Effect of food restriction on reproduction and lactation in house mice mated post partum.

Primiparous, post-partum mated BALB/c bom inbred mice were allowed to raise litters of 6 young until Day 22 of lactation: 11 of 25 females were restricted to 60% of food consumption of ad-libitum fed dams after stud male removal at Day 2 of lactation. Since weight gain of restricted females during lactation was not inhibited and infanticidal behaviour was not enhanced, food deprivation can be considered to have been relatively mild. However, none of the food-restricted dams gave birth to a second litter whereas 12 of the 14 ad-libitum fed mice littered. This pregnancy failure is suggested to be due to implantation failure or abortion shortly after implantation, which is attributed to maternal manipulation rather than to immediate consequences of energetic demands of lactated young. The dynamics of the weight changes of dams and young suggest that milk production in suckling house mice drops most markedly between Days 17 and 18 of lactation, irrespective of whether the dams are non-pregnant, pregnant, or food-restricted.