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The Concentration of Estradiol-17ß in Bovine Semen^1,2,

Texas A&M University Agricultural Research and Extension Center, Overton 75684 and Texas A&M University, College Station 77843

Abstract

This study was conducted to evaluate the influence of age, breed, epididymectomy and semen processing on the concentration of estradiol-17ß (E₂) in bovine semen. Semen was collected either by electroejaculation or with an artificial vagina. Neat semen samples were stored at –20 C until analysis. Processed, frozen semen and an egg yolk-citrate semen extender were obtained from a commercial semen processing firm and stored in liquid nitrogen at –196 C. The concentration of E₂ in semen was determined by radioimmunoassay. Semen from mature (>24 mo), fertile Brahman (n=19), Brangus (n=16), Charolais (n=29), Holstein (n=15) and Santa Gertrudis (n=25) bulls was analyzed for E2 concentration, and no difference (P>.10) between breeds was found. There was no difference (P>.10) in seminal E2 con- centration between mature, fertile bulls (n=104) and epididymectomized bulls (n=22). In semen collected from prepuberal (12 to 16 mo, n=21), peripuberal (17 to 20 mo, n=17) and mature (>24 mo, n=19), Brahman bulls, the mature bulls had a lower (P<.01) semen E₂ concentration than peripuberal and prepuberal bulls. There were no differences (P>.10) in seminal E₂ concentration among peripuberal Angus (n=8), Hereford (n=8) and Brahman (n=17) bulls. Analysis of the processed semen showed similar (P>.10).seminal E₂ concentrations among English-European beef (n=6), dairy (n=3), dairy x beef (n=9), Bos indicus as well as Bos indicus cross (n=13) and tropically adapted Bos taurus (n=12) bulls. The egg yolk-citrate semen extender contained 397 ± 5 pg E2/ml and egg yolk contained 989 ± 96 pg E₂/ ml. When the extender value was subtracted from the mean concentrations of E₂ in the extended semen, a range of 0 to 117 pg/ml could be attributed to seminal E₂. Results of this study indicate that prepuberal bulls have a higher concentration of E₂ in their semen than do mature bulls, and there are no breed differences in seminal E₂ concentrations. In addition, the E₂ found in semen does not come directly from the testes. Egg yolk-citrate semen extender contains a high level of E₂ as does whole egg yolk, which results in E₂ levels in extended semen that are higher than those in neat semen.

¹ Journal paper TA 19208, Texas A&M Univ. Agr. Exp. Sta.

² The authors wish to thank Norm Parish of the King Ranch for supplying Santa Gertrudis semen and Charles Golightly of COBA for supplying semen extender.

³ Dept. of Anim. Sci.

⁴ Dairy Breeding Research Center, The Pennsylvania State Univ., University Park 16802.