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Hormone Induction of Lactation

in Cows

Piglets suckling a sow.

Hormonal Induction of Lactogenesis

Lactation can be induced in nonpregnant animals by injection of appropriate hormones. This usually involves stimulating some degree of mammary growth by injections of high levels of estrogen and progesterone (see Mammary Gland Development Resources - Cases B for the role of estrogen and progesterone in mammary growth), followed by some combination of the glucocorticoid and prolactin component of the lactogenic complex.

For cattle, the cow must have been dry for 30 days or more for the hormonal induction to have a good chance of being effective. The injection schedule generally involves several days (generally 7 days) of high levels of estrogen plus progesterone, followed by some means of increasing endogenous PRL, then followed by glucocorticoid injections. This is usually a 3 week period of hormone treatment in total. On day 21, cows are milked regardless of how much udder development they appear to have. Milk production level increases more gradually than when the cow calves naturally. From the Mammary Gland Development Resources, recall the importance of milk removal (nursing) in stimulating mammary growth after parturition and during lactation. Repeated milk removal also is critical to induction of lactation with hormones. This method is not effective in all cows. Some cows do not respond at all. In addition, the level of production reached is generally lower than might be expected if the cow gave birth and started lactation naturally. More recent work indicates that injection of bovine somatotropin (BST; growth hormone) after initiating lactation can enhance milk production.

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