The Experimental Induction of Growth of the Cow's Udder and the Initiation of Milk Secretion

The purpose of this study was to determine the optimum amounts of two ovarian hormones and their synergism for growth of the udders of he.lfers that had failed to conceive.Maximum daily milk production attained when lactation was initiated by means of the estrogenic hormone was used as the index of udder growth.The udder growth and milk secretion that was stimulated closely approached that which might have been obtained had the heifers calved normally.Practical use of this method of inducing growth and lactation will be dependent upon the development of methods of oral administration of the hormones.Editor.As a result of extensive research with experimental animals, it has been shown that the ovarian hormone, estrogen, will stimulate the growth of the mammary gland duct system of gonadectomized animals comparable to that observed in sexually mature animals (28).However, to stimulate the growth of the lobulealveolar system comparable to that observed at the end of pseudopregnancy or the middle of pregnancy, it was found necessary to inject a combination of estrogen and progesterone (28).In recent work with crystalline ovarian hormones, the importance of the proper ratio of these two hormones for optimal growth of the lobule-alveolar system has been pointed out (28).In the rabbit, Seharf and Lyons (18) observed optimal synergism when 24 to 96 7 of estrone were administered with 1 rag. of progesterone daily for 25 days.This represents a ratio of estrogen to progesterone of 1:11 to 42.Yamamoto and Turner (28) recently confirmed their observations.However, in other experimental animals, the ratio of the two hormones for optimal synergism was observed to be of the order of 1 part of estrogen to 1,000 or more parts of progesterone, as shown in the mouse (4, 19, 27); rat (4), and dog (21).In spite of the extensive research work indicating the synergism of the two ovarian hormones for complete lobule alveolar growth of the mammary gland of experimental animals, comparable studies with goats have led to a variety of conclusions in regard to the need of progesterone for lobule-alveolar growth.Mixner and Turner (12) reported that the daily injection of 20-30 rag. of