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Biological Assay of Beef Steer Carcasses for Estrogenic Activity Following the Feeding of Diethylstilbestrol at a Level of 10 Mg. Per Day in the Ration¹

Missouri Agricultural Experiment Station²

Abstract

A control lot of 10 Hereford steers and a lot of 20 animals receiving 10 mg. daily of diethylstilbestrol were fed for 148 days. The diethylstilbestrol was withdrawn 44 hours before slaughter. Composite samples of 21 tissues, organs, depot fat, digestive tract and blood from the two groups were obtained for bioassay for residual estrogen.

A comparison was made to determine the effect of graded doses of diethylstilbestrol added to control rib-eye tissue using as assay animals young sexually mature ovariectomized mice with normal weanling mice. The sensitivity of the assay method was about 2 parts per billion. Ovariectomized mice were used in all assays.

Using the comparison of the uterine stimulation induced by the control and experimental tissues and by the effect of added diethylstilbestrol, it was concluded that the edible red meat, rib-eye, neck trimmings and tongue did not contain detectable residual estrogen. The liver, heart, spleen, and brain also did not contain detectable amounts of hormone. The kidneys showed evidence of estrogen to the extent of 4 parts per billion while the lungs indicated the presence of 10 to 12 parts per billion of residual estrogen. The depot fat at 25 and 50 percent levels and the blood showed no evidence of estrogen nor did the various parts of the digestive tract.

The average length of the teats of the diethylstilbestrol-fed steers were about double the length of the controls and small amounts of colostrum was frequently observed in the cisterns.

The feed fed the steers was bioassayed. The control feed showed some estrogen activity but the feed containing 5 mg. per pound and a commercial feed caused great uterine stimulation.

Dairy cows fed diethylstilbestrol at the 10 mg. level showed as much estrogenic activity in the dried feces as was present in the feed.

¹ This study was aided by a grant from the National Live Stock and Meat Board. Contribution from the Department of Dairy Husbandry, Mo. Agr. Exper. Sta. Journal Series No. 1544. Approved by the Director.

² Columbia.