Melengestrol acetate (MGA), with CAS number 2919-66-6, is a synthetic progestogen steroid. It is a white to off-white crystalline powder that is practically insoluble in water but soluble in organic solvents such as chloroform and acetone. Chemically, it is an acetate ester derivative of melengestrol. Its primary and well-established application is in veterinary medicine as a feed additive for livestock, specifically for the suppression of estrus (heat) in heifers intended for feedlot beef production. By controlling the estrous cycle, it promotes more uniform weight gain and feed efficiency. It is not approved for use in lactating dairy cows. While its main use is in animal husbandry, as a synthetic progestin, it falls under the broad category of endocrine and metabolic agents. The compound is typically administered orally via feed. Regulatory controls are in place for its use in food-producing animals to ensure the safety of the food supply, with established withdrawal periods before slaughter.