During late lactation maternal food intake reaches a plateau, indicating that the female is limited in her sustained energy intake. We recently suggested that this limit is mediated by the capacity to dissipate heat. This is consistent with the fact intake at peak lactation and pup growth increase in cold (8 °C) and decrease in hot (30 °C) conditions. Moreover shaving mice at peak lactation allows them to increase their food intake and raise larger pups. A potential mechanism causing these effects is that suckling pups reduce the female's capacity to dissipate heat, causing her body temperature to rise. We have instrumented mice with temperature transmitters and followed their body temperatures in relation to their suckling behaviour during peak lactation. These studies reveal that lactating females are under chronic hyperthermia. The patterns of body temperature change during suckling bouts do not support an interpretation that overheating is caused by the suckling pups preventing heat loss. Heat dissipation problems therefore occur because of the continuous heat production resulting from milk synthesis and the specific dynamic action (SDA) of the diet. The heat dissipation limits hypothesis predicts that when given a choice lactating females should avoid diets with a high SDA. Moreover, when not given a choice intake, milk production and offspring growth should all depend on SDA. I will present some unpublished data testing these predictions in cats and mice. Generally the predictions hold up in a qualitative fashion, but the quantitative details reveal some additional complexity.
|Number of pages||1|
|Journal||Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology|
|Issue number||2, Suppl.|
|Publication status||Published - Jun 2009|
|Event||Annual Main Meeting of the Society of Experimental Biology - Glasgow, United Kingdom|
Duration: 28 Jun 2009 → 1 Jul 2009