In the 2002 cohort, fewer heifers had inter-oestrus periods shorter than 16 days
during the first breeding season than in the 2003 cohort (32/106 vs. 36/73, P = 0.012),
whereas the proportion of inter-oestrus periods longer than 24 days was similar (19/106
vs. 7/73, P = 0.136). Median days to first oestrus, to first pregnancy and to first calving