The effects of unilateral castration and vasectomy on the weight and microscopic appearance of the contralateral testis and on the blood levels of testosterone, LH and FSH, were studied in German Fleckvieh bulls. Testicular weights were higher in hemicastrated bulls (P < 0.01) and unilaterally vasectomized bulls (P < 0.05) when compared to controls, 377 ± 45g (x ± s, N = 4 and 281 ± 12g, N = 4 vs 226 ± 38g, N = 3, respectively.
Testosterone concentrations were higher during the weeks 14 to 22 after surgery in both treated groups. LH levels were not different from controls, but FSH levels increased significantly (P < 0.01) two weeks after hemicastration and unilateral vasectomy.
Different factors appear to regulate the LH and the FSH concentrations in bulls. The increase of FSH after hemicastration may indicate a reduced production of inhibin or an inhibin-like substance from the testes, and a similar increase after unilateral vasectomy suggests that this substance may be resorbed distal to the testes.