Records on 491 Hereford cows were analyzed to estimate heritabilities of some measures of reproduction in the first calving. Estimates were obtained from paternal half-sibs by both analysis of variance (ANOVA) and chi-square (X2)- Heritabilities estimated from ANOVA and from X2 for binary variables were corrected to a normal basis (ANOVA—C and X2 —C). For calving rate at 2 years of age the heritabilities were .01 ± .02 (ANOVA), .02 ± .04 (ANOVA-C), .13 ± .09 (X2) and .22 ± .12 (X2—C). When heifers that failed to calve at both 2 and 3 years of age (barren) were excluded from the data, estimated heritabilities were .21 ± .13 (ANOVA), .45 ± .19 (ANOVA-C), .22 ± .14 (X2) and .48 ± .20 (X2 —C). The heritability of barrenness was .0 ± .04 (ANOVA), .16 + .10 (X2) and .33 ± .15 (X2 —C). Analysis of perinatal survival evaluated as a characteristic of the dam yielded heritability estimates of .64 ± .21 (ANOVA), 1.25 ± .35 (ANOVA—C), .61 + .25 (X2) and 1.19 ± .34 (X2 —C). Heritability of services per conception for the first calving was estimated at .64 ± .29.
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Milagres et al. (1979) studied this question.