Selection for postweaning gain in rats: II. Correlated response in reproductive performance.

Abstract

Reproductive performance was evaluated on lines of rats selected 34 generations for up (U) and down (D) 3- to 9-wk weight gain and from a control (C). Direct response to 3- to 9-wk weight gain was 16% in U and -8% in D lines. Inbreeding was similar among lines. Both selection lines were poorer in percentage of fertile pairs than the C line, especially so in D (P less than .10). The lines differed (P less than .05) in litter size born with means of 11.4, 10.4 and 9.6 for U, C and D, respectively. The significant positive correlated response in litter size corresponded to that expected from intraline association with female body weight. Selection for increased postweaning gain resulted in 5% earlier age but little change in weight at vaginal opening. The D line was similar to C in age, but 7% lighter in weight at vaginal opening. The U line was significantly higher (14, 12 and 69%) for ovulation rate, number of fetuses and post-implantation losses, but not for pre-implantation losses. The D females were similar to C females in all components of litter size. Males of all lines were similar in age at first mating, but U males were 22% heavier than C males in weight at first mating. A positive correlated response in weight of testes at 91 d of age disappeared when adjusted for intraline association with body weight.

• Authors: J G Rios, M K Nielsen, G E Dickerson
• Journal: Journal of animal science (J Anim Sci) Vol. 63 Issue 1 Pg. 46-53 (Jul 1986) ISSN: 0021-8812 [Print] United States
• PMID: 3733576 (Publication Type: Comparative Study, Journal Article)

Topics

• Animals
• Body Weight
• Female
• Fertility
• Litter Size
• Male
• Organ Size
• Ovulation
• Pregnancy
• Pregnancy, Animal
• Rats (physiology)
• Selection, Genetic
• Sexual Behavior, Animal
• Testis (anatomy & histology)
• Weaning