Variability of the postpartum recovery of sexual activity of Charolais cows

Data (n = 1725) were collected from 613 primiparous and multiparous Charola is cows managed in an experimental herd over a 10-year period. The objectiv es of the study were to describe the variability in the re-establishment of postpartum reproductive activity. The duration of the postpartum anoestrus period was estimated from progesterone concentrations in weekly blood samp les, and from daily detection of oestrous behaviour. Oestrous behaviour was first observed 71.9 days (+/- 27.2 S.D.) post-calving, and a first positiv e progesterone concentration (greater than or equal to 1 ng/ml) was observe d at 68.7 days (+/- 25.5 S.D.). There were differences in the chronology of these events: a first positive progesterone test was detected before she f irst oestrus in 51% of the cases. The duration of the first oestrous (25.6 +/- 16.4 days) and ovarian (2.8 +/-0.9 weeks) cycles varied according to th e chronology of the events. Year and period of calving, calving difficulty and parity (interacting with suckling status) significantly affected the du ration of the postpartum anoestrus period. These results also showed an imp ortant effect of individual female on the duration of postpartum anoestrus with a repeatability of 37% for the interval to the first oestrus and 60% f or the interval to the first positive progesterone test. (C) 2001 Elsevier Science BN. All rights reserved.