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Efficiency of Growth in Mice with a Major Gene for Rapid Postweaning Gain

University of California, Davis 95616

Abstract

Previous research in this laboratory demonstrated the existence of a major gene (hg), inherited as a homozygous recessive, which increases postweaning growth by 40 to 50% in C57B1/6 mice (Ch) compared to the same genetic stock without the major gene (CH). Although its effect has not been previously evaluated, this single recessive allele is also in a line of mice selected for rapid postweaning gain for over 70 generations. Gh represents that line of mice with the major gene for growth (hg) in the growth-selected background and GH the growth-selected background without the major gene. Total body weight, daily weight gain, feed consumption and gain/feed, measured daily from 21 to 42 d of age, were all significantly greater (P<.01) in the two lines with the hg/hg genotype (Ch and Gh) compared with their respective control lines (CH and GH). Differences in body composition at 42 d of age between CH compared with Ch and GH compared with Gh were accounted for by difference in,body weight. Gross and net energetic efficiency, calculated assuming a similar maintenance energy requirement, were improved (P<.01) in Ch and Gh compared to CH and GH, respectively. The results demonstrated that hg influences growth in growth-neutral and growth-selected backgrounds. The gene also alters energy metabolism by increasing energetic efficiency of growth and(or) decreasing maintenance energy requirement.

¹ Dept. Anim. Sci.

² On leave from Canadian Dept. of Agr., Res. Sta., Lennoxville, Quebec, Canada.

³ Supported by the Summer Undergraduate Affirmative Action Research Program sponsored by the College of Agr. and Environ. Sci. Present address: 4615 Russell Ave., Los Angeles, CA.