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Growth of the Calf Udder Using DNA as an Index^{1, 2,}

Department of Dairy Husbandry, University of Missouri, Columbia

ABSTRACT

Nine dairy calves were administered subcutaneously 30 µg. estradiol benzoate (EB) and 30 mg. progesterone (P) daily, starting at 2 mo. of age. Each month, the EB and P were increased 10 µg. and 10 mg., respectively. Three calves were sacrificed after 2, 4, and 6 mo. of treatment. The udders were removed and the glands in each quarter were dissected free of the surrounding fatty tissue, cut up into tiny pieces, and the fat and water extracted. The dry, fat-free tissue was then analyzed for the content of DNA per milligram. The total DNA in each quarter of the calf's udder was quite similar, but considerable variability was observed in either total DNA per udder or per 100 lb. body weight. In comparing the group injected for 4 mo. with the 2-mo. group, a marked increase in growth (DNA) was observed. It is believed that the DNA method will serve as a satisfactory method of quantitative estimation of normal and experimental gland growth in calves.

¹ Contribution from the Missouri Agricultural Experiment Station, Journal Series No. 2285. Approved by the Director.

² Aided in part by a grant from the U. S. Atomic Energy Commission [Contract No. AT (11-1)1301]. Syntex Animal Products Co. has generously contributed ovarian hormones.