Genetic, Heterosis, and Maternal Effects on Voluntary Water Consumption in Mice

Managing natural resources, particularly water, is a prominent issue for animal agriculture. Due to such challenges livestock producers are always looking to lessen resource consumption. The objective of our study is to contribute to improving water management by identifying the genetic control of water consumption. In standard laboratory conditions inbred mouse strains, with unaltered kidney function, show a three-fold range of daily water consumption. This study used C57BL10J (BL n=47) and C57BRCDJ (BR n=29) mice, identified to be in the high and low end of this range, respectively, and reciprocal F1 crosses. Using BL males x BR females (F1BR n=21) and BL females x BR males (F1BL n=92), daily consumption data were collected for four days during the 4^th, 5^th, and 6^th wk using custom water bottles. Animals were weighed at the beginning of the 4^th, 5^th, and 6^th wk, and at the end of the 6^th wk. Consumption data were corrected for metabolic body weight (wt^0.67) prior to analysis, so water consumption is expressed in milliliters consumed per gram of metabolic body weight per day. Final weight was the dependent variable for weight analyses. Dependent variables were fitted to a mixed model including the effects of sex, strain, and their interaction with sire within strain fitted as a random effect. Orthogonal contrasts were used to test the direct genetic, maternal genetic, and heterosis effects. An interaction (P<0.0001) was observed between sex and strain with females in all strains consuming more than males and the sex difference increasing as consumption increased among strains. Animals from the BR strain consumed 40% more water per day (P<0.001) than BL animals (1.32 vs 0.65 ml/g, respectively). A maternal effect (P<0.03) was observed as F1BL consumed about 9% less water per day than F1BR (0.95 mL/g vs 1.01 ml/g, respectively). Finally, a heterosis effect of -4% was observed for water consumption (P<0.10). For final weight, BR animals (20.6 g) were heavier (P<0.02) than BL animals (19.2 g). No maternal effect for weight was observed. Animals from the reciprocal F1 crosses showed an increase in body weight of nearly 10% over pure strains (P<0.001). These strains form the foundation stock of an experiment to isolate genes influencing water consumption by reciprocal backcrossing and selection.