Genetic, maternal, and heterosis effects on voluntary water consumption in mice

In standard laboratory conditions, inbred mouse strains with normal kidney function show a 4-fold range of daily water consumption. This study uses two strains of inbred mice identified as high and low consumers, their reciprocal F1 crosses, and inter se bred F2s. Daily consumption data were collected on 607 animals for 4 d during the 4th, 5th, and 6th wk using custom water bottles. Animals were weighed at the beginning of the 4th, 5th, 6th, and 7th wk. Consumption data were corrected for metabolic BW (Bwt0.67) prior to analysis, so units of water consumption are expressed in mL consumed per gram of Bwt0.67 per day. Variables BW and water consumption were fitted to a mixed model including the effects of sex, strain, and their interaction with sire within strain fitted as a random effect. Contrasts were designed to test the direct genetic, maternal genetic, individual heterosis, and maternal heterosis effects. An interaction (P < 0.0001) was observed between sex and strain so all analyses were conducted separately for each sex. C57Brown/CDJ animals (Brown) consumed more water than C57Black/10J animals (Black) (P < 0.0001). A maternal effect (P = 0.036, P = 0.029) was observed in males at the 4th and 5th wk as F1 animals with a Black dam (F1Black) consumed less than F1 animals with a Brown dam (F1Brown) males. No significant heterosis effect was observed for water consumption. For weight analysis, Black animals were significantly larger than Brown animals at 28 d (males P = 0.004, females P = 0.026), but no difference was observed the remainder of the trial. Further, F1Brown females were significantly smaller than F1Black females at 28 d (P < 0.0001) and F1Brown males tended to be smaller than F1Black males (P = 0.078). Animals from the reciprocal F1 crosses showed an increase in birth weight (P < 0.0001) over pure strains. These strains form the foundation stock of an experiment designed to isolate genes influencing water consumption by reciprocal backcrossing and selection.