Puberty in Charolais heifers in relation to growth rate. 2. Genetic variability

The genetic variability of age at puberty estimated by the age at the first observed oestrus and the age at the first positive progesterone test was d escribed for 351 Charolais heifers, the progeny of 60 sires, The relationsh ip between age at puberty and growth rate of the heifers was also studied. Estimates of heritability were 0.34 for the age at the first observed oestr us and 0.27 for the age at the first positive progesterone test. The geneti c correlation between these two criteria was high (r(g) = 0.94). Negative e nvironmental relations existed between age at puberty and growth rate of th e heifers until 1 year of age and with mature weight. The genetic relations hip between puberty criteria and growth rate was also negative. Heifers wit h a high genetic potential for growth also had a high potential for an earl y puberty. Puberty age criteria were, however, independent of the degree of weight maturity at 1 year of age but negatively related to adult weight. W eight maturity at the first oestrus was highly correlated (r(g) = 0.70) wit h age at the first oestrus. ((C) Elsevier / Inra).