Growth of the Calf Udder Using DNA as an Index

Abstract

Nine dairy calves were administered subcutaneously 30 [mu]g estradiol benzoate (EB) and 30 mg progesterone (P) daily, starting at 2 months of age. Each month, the EB and P were increased 10 [mu]g and 10 mg, respectively. Three calves were sacrificed after 2, 4, and 6 months of treatment. The udders were removed and the glands in each quarter were dissected free of the surrounding fatty tissues, 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 satisfactorily method of quantitative estimation of normal and experimental gland growth in calves.