ESTIMATES OF HERITABILITIES AND GENETIC AND ENVIRONMENTAL CORRELATIONS FOR LEFT-SIDE AND RIGHT-SIDE UTERINE CAPACITY AND OVULATION RATE IN MICE

Heritabilities for and genetic and environmental correlations between uterine capacity, ovulation rate, and body mass (BM) were estimated in mice. Uterine capacity was defined as the number of fetuses (LUC or R UC for left or right side) in one uterine horn for unilaterally ovarie ctomized females. Ovulation rate (corpora lutea, LCL or RCL for left o r right ovary) was measured on the remaining single ovary in these sam e females. Data on 1,931 mice from four selection populations were use d. Left ovulation rate and LUC were measured on 958 animals, and RCL a nd RUC of another 972 animals were recorded. Genetic and environmental variances and covariances were estimated simultaneously using an anim al model with a multiple-trait, derivative-free, restricted maximum-li kelihood procedure. Averages for heritability and correlation estimate s derived from separate analyses of the selection populations are pres ented below. Heritability of LUC was higher (.33 +/- .06) than that of RUC (.19 +/- .02). Heritability of LCL and RCL ranged from .17 +/- .0 3 to .27 +/- .06, and heritability for BM was .65 +/- .05. The genetic correlation between LUC or RUC and LCL or RCL ranged between .43 +/- .29 and .68 +/- .05, and between LUC and RUC was .92 +/- .05. Body mas s had a higher genetic correlation with LCL and RCL (.70 +/- .12 and . 93 +/- .02) than with LUC and RUC (.37 +/- .05 and .47 +/- .12). Envir onmental correlations between LCL and LUC and RCL and RUC were .32 +/- .09 and .36 +/- .05, respectively.