Application of progesterone measurement for fertility control in Korean native cattle

Studies were conducted in Korean native cattle (Bos taurus coreanae) to determine the age and bodyweight at puberty, and to determine the post-partum anoestrus intervals based on plasma progesterone profiles, rectal palpation and oestrus observation. Korean native cattle reached puberty at 11.3 months of age and at 188 kg bodyweight as determined by progesterone profiles, but oestrus was not detected until 3 months later, at a bodyweight of 215 kg. Prolonged post-partum anoestrus occurred in 40% of small holder's cows, where animals were tethered and fed hay and rice straw, whereas its incidence was only 7% in a well managed herd that was grazed and housed. Plasma progesterone profiles were used to monitor ovarian activity post-partum in standard fed cows (n=44) and restricted fed cows (n=20). In standard fed cows 81.8% showed luteal activity by 50 days post-partum, compared to 55% in restricted fed cows. Approximately 40% of cows in both groups had shows observable oestrus by this time. This study indicates that one or more ovulations occurred before pubertal heifers and post-partum cows showed overt oestrous behaviour. It is concluded that improved management and feeding practices should result in improved reproductive performance. (author). 15 refs, 2 figs, 3 tabs