Drug approved for cow estrus synchronization

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An old drug gained a new approval to aid artificial insemination in cows, and federal regulators have updated guidance to reflect the change.

In July, Food and Drug Administration officials published a letter to bovine veterinarians that Cystorelin (gonadorelin), a prescription gonadotropin-releasing hormone product, can be administered with cloprostenol sodium to synchronize estrus in cows raised for meat or milk. It is the fourth such synchronization product that has been approved but only the second that can be used in beef cows.

Agency officials also updated guidance for cattle producers on the estrus cycle and drugs used to control and synchronize estrus. The original guidance had been available since January 2017.

Cystorelin, which is made by Merial, has been approved for use in treating ovarian follicular cysts in dairy cattle since 1978. The FDA guidance on cattle estrus explains that drugs in the gonadorelin class mimic natural hormone release from an animal's hypothalamus before ovulation, prompting release of other hormones that cause ovarian follicle development and ovulation.

The three other gonadorelin drugs available for estrus synchronization are Factrel from Zoetis, Gonabreed from Parnell Technologies, and Fertagyl from Intervet.