Effect of fur removal on energy budget in lactating KM mice supporting additional pups

The aim of this study was to understand the factors limiting maximum sustainable energy intake and metabolic rate (SusEI/MR) during lactation.Maternal body mass,food intake,litter size and litter mass throughout lactation and basal metabolic rate (BMR) and thermal conductance during late lactation were measured in dorsally shaved KM mice supporting additional pups.BMR within the thermal neural zone of this species was determined using a closed-circuit respirometer.The present results showed that there were no significant effects of litter size on the maternal body mass,food intake,thermal conductance,BMR and litter mass during lactation.Shaved mothers had 13.8% higher asymptotic food intake (P0.001),18.1% higher BMR (P0.01) and 30.8% higher thermal conductance (P0.01) than did non-shaved controls.However,fur-removal had no significant impact on maternal body mass,litter size and litter mass.Litter size was significantly positively correlated with litter mass,but negatively correlated with mean pup body mass at weaning.There were also positive correlations between BMR and maternal body mass and litter mass.It suggested that SusEI/MR during lactation was constrained in KM mice.Fur-removal significantly increased the capacity to dissipate heat,but had no effect on reproductive output.The current study provided support for the "peripheral limitation hypothesis" but argued against the "heat dissipation limitation hypothesis"