Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: March 25, 1997
Publication Date: N/A
Technical Abstract: Onset of puberty (sperm production) occurs at a much younger age (56-84 d) in Chinese Meishan boars than in conventional boars (120-180 d). Throughout development, Meishans exhibit markedly elevated (two- to ten-fold higher) concentrations of serum FSH, LH and androgens compared to conventional boars. An early postnatal peak (1-4 wk of age) in serum gonadotropins and androgens occurs in both types of boars, but Leydig cell size becomes four-fold larger in Meishans than in conventional boars, and two-fold larger Leydig cell size is maintained during establishment of sperm production and at maturity. Establishment of the blood-testis barrier and cessation of Sertoli cell proliferation occurs much earlier in Meishan (40 d) than in conventional boars (100 d). Indeed, testis size in Meishans is only one-half that of conventional boars at maturity, and number of Sertoli cells is markedly reduced in Meishans. However, Meishan testes exhibit reduced degeneration of germ cells and spermatids during spermatogenesis, and spermatogenic efficiency per Sertoli cell in Meishans is double that in conventional boars. At maturity, Meishan pituitaries have greater mass, larger gonadotrophs, higher content of FSH, and greater expression of genes for FSH and LH subunits than found in conventional boars. The high levels of serum gonadotropins in the Meishan exhibit a typical postcastration rise, respond to GnRH stimulation and are suppressed by gonadal steroids, indicating that the hypothalamo-pituitary-gonadal axis functions normally but with much higher set points in Meishan boars. These unusual endocrine and physiological attributes in boars of the highly prolific Meishan breed offer a unique model for further investigation of factors influencing male reproductive function.