Limits to sustained energy intake XXXII: Hot again: dorsal shaving increases energy intake and milk output in golden hamsters (Mesocricetus auratus)

Abstract

Golden hamsters have four times the body size of mice, raise very large litters and are required to produce big quantities of milk during the 18 days lactation period. We have previously proposed that they may be prone to being limited by their heat dissipation capacity. Studies where lactating females are shaved to elevate their heat dissipation capacity have yielded conflicting data so far. With their short pregnancy of ca. 18 days, the large litters and the reported higher skin temperatures they may serve an ideal model as to elucidate the role of epilation for energy budgets in lactating mammals. We shaved one group of lactating females dorsally on the 6th day of lactation, and tested, if the elevated heat dissipation capacity would enable them to have higher energy intakes and better food to milk conversion rates. Indeed, we observed that females from the shaved group had 6% higher body masses and 0.78° C lower skin temperatures than control females during lactation. When focusing on the phase of peak lactation, we observed significantly higher (10%) gross energy intakes of food and 23.4% more milk energy output in the shaved females resulting in 3.3g higher individual pup weights. We conclude that shaving off the females’ fur, even though restricted to the dorsal surface, had large consequences on female energy metabolism in lactation and improved milk production and pup growth in line with our previous work on heat dissipation limitation. Our new data from golden hamsters confirm heat dissipation as a limiting factor for sustained metabolic rate in lactation in some small mammals and emphasize the large effects of a relatively small manipulation such as fur removal on energy metabolism of lactating females.