The Contribution of Changes in Milk Delivery to the Prolongation of Lactational Infertility Induced by Food Restriction or Increased Litter Size

Food restriction during lactation suppresses Kiss1 mRNA expression and kisspeptin-stimulated LH release in rats

“…Lactation is also associated with a huge metabolic demand due to the production of milk, and despite food consumption of w300% of that of virgin rats, lactating dams enter a state of negative energy balance. Although it has long been known that food availability plays a key role in the maintenance of fertility, the negative energy balance experienced by lactating rats is not necessary for the maintenance of lactational anovulation (Woodside 1991, Woodside & Popeski 1999. However, food restriction in lactating rats for the first 2 weeks postpartum (pp), at a level of 50% of the ad libitum daily ration, prolongs the duration of lactational anovulation by w7 days (Woodside 1991).…”

Ligation of the Uterine Artery and Early Postnatal Food Restriction – Animal Models for Growth Retardation

“…Since the rat is relatively immature at birth compared with humans [11], an early FR model may provide more appropriate information for the last part of human pregnancy, however, in this case the role of the placenta is excluded. A temporary FR during the suckling period can be achieved by litter enlargement or by undernourishing the mother by giving a low-protein diet during lactation, both entailing a decrease in energy availability and a consequent undernutrition of the pups [12, 13]. During this early postnatal period, when the developing body still has its plasticity, malnutrition is a serious challenge and may affect growth and development of different organs [14].…”

Many mouths to feed: The control of food intake during lactation

“…Suppressing PRL release with bromocryptine suppresses the food intake of GC females to levels seen in cycling females and restoring PRL levels by direct icv infusion restores food intake (Woodside and Popeski, 1999). These data suggest that PRL acts centrally to contribute to the hyperphagia of lactation.…”

“…Most of the studies evaluating the contribution of suckling independent of milk delivery to food intake during lactation have used one of two models: the acute resuckling model (Smith and Grove, 2002), or the galactophore-cut or ligation model (Cotes and Cross, 1954;Fleming, 1976;Woodside and Popeski, 1999). In the acute resuckling model, lactation is established and then during the second week of lactation the young and mother are separated for 48 h. Dams readily accept and suckle their young when the dyad is reunited and because suckling is reestablished rapidly prior to the restoration of full lactation there is a period of time during which one can assess the acute effects of suckling independent of the energetic demands of lactation.…”

“…The offspring continue to suckle at nipples that do not deliver milk and in order to maintain the health of the pups cross fostering between galactophore-cut and intact foster mothers. The result of the maintenance of suckling stimulation is that circulating prolactin (PRL) levels in GC females are similar to those of intact lactating females as is the length of lactational infertility (Woodside and Popeski, 1999). GC females differ from intacts, however, because they do not lose fat during the postpartum period and maintain high circulating leptin levels.…”