Therefore metabolic differences in prepubertal calves were later reflected by altered reproductive function during the first lactation.

In the first lactation, milk energy output for the first 120 days of lactation was also calculated.

These metabolic parameters were subsequently related to physical characteristics at puberty and to ovarian function during the first lactation.

Heritability estimated with the repeatability model was 0.27 and the coefficient of repeatability for first lactation TDMF was 0.66.

The fatty acid composition of milk from 4 female transgenic founders was analyzed on d 7, 14, and 30 of their first lactation.

A highly significant positive relationship was established between the GH peak measured 10 min post-GRF challenge and 120-day milk energy values in the first lactation.

Genetic parameters for test-day milk flow (TDMF) of 2175 first lactations of Holstein cows were estimated using multiple-trait and repeatability models.