Synchronisation of Oestrus in Dairy Cows Using Progesterone Administered by "controlled Internal Drug Release" (cidr) Devices

The proportions of cows showing oestrus during the first 5 days were 22%, 78% and 87X, and by 25 days were 85%, 92% and 98% for groups 1, 2 and 3 respectively. In group 3, 83% of animals had exhibited oestrus and 49% subsequently conceived to A.I. at the fixed time of 63h. Pregnancy rates after 25 days of mating as determined by rectal palpation were 46%, 62% and 64% for groups 1, 2 and 3 respectively. These results demonstrate that the CIDR is an effective device for synchronisation of oestrus in dairy cows, and when used in combination with luteolytic prostaglandins this synchronisation is sufficiently precise for successful A.I. at a fixed time.