Growth hormone treatment of breeding bulls used for artificial insemination improves fertilization rates

To evaluate new therapeutical concepts for male subfertility, we tested the effects of exogenous recombinant bovine growth hormone (rbGH) on various e ndocrine and metabolic parameters both in blood and in seminal plasma of bu lls. Sperm quality was assessed morphometrically and by monitoring the numb er of successful artificial inseminations (AIs) defined as non-return rates (NRR). Aliquots of 450 semen samples were used from each bull and each exp erimental period (4 wk before, 14 weeks during and 6 wk after treatment). S ix out of ten sires (average age 8.4 years) were treated every two weeks wi th 640-mg depot formulated rbGH (Eli Lilly). Four bulls received vehicle on ly. Blood plasma bGH, IGF-I, insulin and glucose concentrations were increa sed with rbGH treatment. In seminal plasma there was no effect of rbGH trea tment on fructose and citrate or on testosterone concentrations. With one e xception, rbGH-treated bulls had greater IGFBP-3 concentrations in seminal plasma. Motility of spermatozoa after freezing and thawing was increased co mpared with pretreatment rates. Most interestingly, the number of successfu l AIs was increased by an average of 6.0% NRR when ejaculates from rbGH-tre ated bulls were used. (C) 2000 Elsevier Science Inc. All rights reserved.