Effects of Caponization on Expression of Gonadotropin-Releasing Hormone-I and Gonadotropin Subunits Genes in Roosters

We evaluated the effects of caponization on mRNA levels of gonadotropin-releasing hormone-I (GnRH-I), gonadotropin subunit and other hypothalamic and hypophyseal peptide genes in male chicken. Thirty roosters (25 d) with similar weight were equally divided into the experimental (capons) and control (sham-operated males) groups randomly. Caponization was performed at 28 days of age and birds were slaughtered at 140 days of age. Caponization resulted in increasing levels of luteinizing hormone β (LHβ) and follicle-stimulating hormone β (FSHβ) mRNA in the pituitary gland and levels of LH and FSH in serum (P<0.05 or P<0.01). There were no significant differences in levels of GnRH-I, Gonadotropin releasing hormone receptor (GnRHR), neuropeptide Y (NPY) and Proopiomelanocortin (POMC) mRNA between the two groups. Capons exhibited lower levels of follistatin (FS), estrogen receptor α (ERα) and higher levels of androgen receptor (AR) mRNA in the pituitary gland compared with sham-operated males (P<0.05). These results suggest that increased LH and FSH concentrations in serum and LHβ and FSHβ mRNA levels in pituitary after castration are not depended on GnRH synthesis. And changed expression of ERα, AR and FS genes in the pituitary gland may be important components of regulating gonadotropin in capons.