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Effects of Implanting Prepuberal Dairy Heifers with Anabolic Steroids on Hormonal Status, Puberty and Parturition

Agricultural Research Council, Institute for Research on Animal Diseases, Compton, Newbury, Berkshire, U.K., RG16 ONN.

Abstract

Potential long term side effects associated with the use of anabolic steroids in the rapid rearing of dairy heifers were assessed. Twenty-seven Friesian heifer calves were allocated to nine blocks of three treatments. One animal, selected at random in each block, was implanted at 16 weeks and again at 31 weeks of age with either 300 mg trenbolone acetate (T), or 140 mg trenbolone acetate plus 20 mg estradiol-17ß (TE), or was sham implanted.

Effects on reproductive function were assessed. Puberty (time of first estrus) was delayed (P<.01) until 52.4 weeks and 59.9 weeks of age in T and TE groups, respectively, compared with controls which reached puberty at 42 weeks. Although conception rate was normal, there was a greater (P<.005) incidence of dystocia with virilization of the clitoris and vulva in the T and TE groups compared with controls. Heifers with dystocia had increased (P<.05) concentrations of progesterone in plasma through the last 10 days of pregnancy compared with heifers that calved normally. There were no such changes in plasma estradiol-17ß concentrations.

Trenbolone and estradiol-17ß were detectable in plasma for approximately 3 months after implantation but had disappeared before the heifers were 1 year old. Concentrations of testosterone and progesterone in plasma were similar in the three groups throughout pregnancy except that testosterone concentrations during 18 to 22 weeks of pregnancy were higher in the TE group compared with that of controls (P<.05).

It was concluded that T and TE should not be used to promote growth in heifers reared for breeding purposes.

¹ The authors gratefully acknowledge the advice of Dr. W. M. Allen, the gifts of Finaplix from Hoechst, U.K., Revalor and antibody to estradiol-17ß from Roussel-Uclaf, Paris, France and the antibody to trenbolone from Dr. B. Hoffman, Munich, Germany. Mr. S. R. Shaw and Mr. A. Patterson are thanked for their statistical analyses.