Meeting Abstract
According to the heat dissipation limitation hypothesis, the extent of heat produced as a by-product of both metabolism and milk production is constraining the amount of food a female can ingest and the efficiency by which she converts nutrients into milk. Our model, the golden hamster (Mesocricetus auratus) produces large litters of 3-16 altricial young and transfers large quantities of milk to them during the 3-weeks lactation period. By breeding golden hamsters at three different ambient temperatures (8°C, 22°C, 30°C) we observed that subcutaneous body temperatures in lactating females were 0.5°C higher than in non-reproductive controls (F1,123=13.6, p<0.01). We also observed that at 30°C lactation comes to a standstill with very low survival of young. Comparing milk energy output, food intake and energy assimilation at three ambient temperatures, we found they were highest at 8°, lowest at 30° and intermediate at 22°C. In the next experiment, we hypothesised that dorsal fur shaving may alleviate the heat stress. We compared energy turnover in shaved and unshaved golden hamsters and their pups. Dorsal shaving females led to an increase in pup growth: with nearly identical mean litter sizes, shaved mothers having lower faecal cortisol metabolites levels also weaned 38.5% heavier litters than litters produced by unshaved golden hamsters.
