Department of Veterinary Medicine, Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan.
Department of Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan.
J Vet Med Sci. 2023 May 3;85(5):551-556. doi: 10.1292/jvms.22-0571. Epub 2023 Mar 16.
Cryptorchid bulls have low economic value owing to the effects of masculinization. Moreover, surgical removal of an ectopic testis is difficult in certain clinical cases. Recently, immunocastration has garnered popularity as a nonsurgical castration method in pig farming; however, the effects of immunocastration on cryptorchid bulls are yet to be yet. Herein, we investigated endocrine changes due to immunocastration in cryptorchid bulls and studied its effectiveness. This study included 13 Holstein bulls diagnosed with cryptorchidism and classified into two groups based on pubertal period: <8 months of age (pregroup) and ≥8 months of age (postgroup). Antigonadotropin-releasing hormone (GnRH) vaccine was used for immunocastration, and two vaccine doses were administered. Blood testosterone and anti-Müllerian hormone (AMH) levels were measured and analyzed for endocrine evaluation. The testosterone levels significantly decreased following the start of immunocastration in both groups, thereby confirming the efficacy of antiGnRH vaccination in cryptorchid bulls. The AMH levels significantly increased in the pregroup with two antiGnRH vaccination, suggesting a compensatory response via the neutralization of GnRH antibodies. The AMH levels did not significantly change in the postgroup, indicating the partial suppression of AMH secretion in Sertoli cells during sexual maturation and failure of Sertoli cell maturation. Thus, we successfully restrained the serum testosterone levels in cryptorchid bulls using antiGnRH vaccine. The testosterone levels are a useful indicator of the immunocastration effect on cryptorchid bulls. Hereafter, a vaccine program that can sustain the castration effect on cryptorchid bulls is necessary.
隐睾公牛由于雄性化的影响，经济价值较低。此外，在某些临床情况下，异位睾丸的手术切除较为困难。最近，免疫去势作为一种非手术去势方法在养猪业中受到欢迎；然而，免疫去势对隐睾公牛的影响尚未得到证实。在此，我们研究了免疫去势对隐睾公牛引起的内分泌变化，并研究了其效果。本研究包括 13 头被诊断为隐睾的荷斯坦公牛，并根据青春期分为两组：<8 个月（前组）和≥8 个月（后组）。使用促性腺激素释放激素（GnRH）疫苗进行免疫去势，并给予两次疫苗剂量。测量和分析血液睾酮和抗苗勒管激素（AMH）水平，进行内分泌评估。两组的睾酮水平在免疫去势开始后均显著降低，从而证实了抗 GnRH 疫苗在隐睾公牛中的有效性。前组在两次抗 GnRH 接种后 AMH 水平显著升高，提示 GnRH 抗体中和后的代偿反应。后组的 AMH 水平没有显著变化，表明在性成熟过程中 Sertoli 细胞的 AMH 分泌部分受到抑制，以及 Sertoli 细胞成熟失败。因此，我们成功地使用抗 GnRH 疫苗抑制了隐睾公牛的血清睾酮水平。睾酮水平是评估免疫去势对隐睾公牛效果的有用指标。今后，有必要制定一种能够维持隐睾公牛去势效果的疫苗方案。
