Induction of Lactation in Pregnant Heifers with 9-Fluoroprednisolone Acetate

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Abstract
Lactation was initiated in dairy heifers during early, mid-, and late pregnancy by injecting 9-fluoroprednisolone acetate (Predef) for about 1 week. Milking was begun on the day of the last Predef injection. Milk yields of 2 early-pregnant heifers given Predef were 0. 25 and 1. 75 lb., respectively, at the 1st milking, and the maximum daily yield attained during the 14-day milking period was 1. 5 and 2. 0 lb. of milk. Two untreated early-pregnant control heifers produced no milk. In 3 late-pregnant, Predef-treated heifers, production at the 1st milking was 10. 0, 11. 0, and 8. 4 lb., respectively, whereas 2 untreated late-pregnant control heifers gave no milk. Milk yields rapidly increased in Predef-treated heifers to a maximum daily average of 28. 3 lb./heifer on the 10th day of milking. Late-pregnant control heifers soon came into milk, as a result of the milking stimulus, and averaged 20. 0 lb. on the 10th day of milking. The data suggest that adrenal cortical steroids are limiting factors for initiation of lactation in pregnant heifers, as in pregnant laboratory animals.