Progesterone profiles and post-partum fertility in dairy cattle in southern Chile

Milk samples were taken at weekly intervals from 77 dairy cows on days 23, 30, 37, 43 and 50 post-partum (pp) in order to monitor ovarian activity through progesterone concentration measurement. Skim milk samples were assayed for progesterone by radioimmunoassay using kits provided through the FAO and IAEA. Oestrus, clinical examinations, treatments, artificial insemination and pregnancy diagnosis were recorded. The profiles of progesterone concentration and oestrus occurrence combined with behavioural and clinical data indicated that the study cows were in the following reproductive states: I - normal, 38%; II - 'silent' oestrus, 12%; III - prolonged luteal activity, 13%; IV - irregular cyclic activity, 23%; and V - anoestrus, 13%. After artificial insemination, 89% (25/28) of normal, 77% (7/9) of silent oestrus, 50% (5/10) of prolonged luteal activity, 82% (14/17) of irregular cyclic activity and 80% (8/10) of anoestrous cows eventually became pregnant either with or without hormone treatment. With the exception of the anoestrous group, these results seem to support the idea that once a week sampling for progesterone over a seven week period pp is sufficient to monitor the ovarian activity and predict the fertility of a dairy herd. (author). 16 refs, 6 figs, 3 tabs