Meeting Abstract

86.6  Friday, Jan. 7  Milk composition of mice divergently selected for Basal Metabolic Rate (BMR) SADOWSKA, J.*; GEBCZYNSKI, A.K; KONARZEWSKI, M.; University of Bialystok; University of Bialystok; University of Bialystok julita.sadowska@uwb.edu.pl

It has been hypothesized that the main factor driving the evolution of high basal metabolic rate (BMR) characteristic for homeotherms was high reproductive performance. We demonstrated a positive correlation between mother’s BMR and growth rate of offspring in lines of laboratory mice divergently selected for BMR. Young nursed by high BMR (HBMR) mothers grow significantly faster than those nursed by low BMR (LBMR) ones, which may suggest between-line differences in quality or quantity of produced milk. To test this we assembled experimental litters, each consisting of 8 pups (4 HBMR+4LBMR) nursed by a high or low BMR female. This allowed us to discriminate between the effect of line-specific pup growth rate and milk quality/quantity. Families were kept in an ambient temperature of 23°C for first 8 days of lactation and then, to increase metabolic load, were moved to 17°C for days 8-14. Milk samples were collected on days 8 and 14. Our preliminary results show between-line differences in fat and lactose, but not in protein content. As shown in other studies, apart from nutritional effect, higher amount of lactose may facilitate calcium absorption from milk and thus increase growth rate of young. Further analyses of milk composition and its effect on growth rate are currently ongoing.