Submitted to: Journal of Reproduction and Fertility
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/1995
Publication Date: N/A
Citation: Interpretive Summary: Sperm production and fertility of boars used for mating are important factors influencing reproductive efficiency in the swine industry, and differences in testis size and structure may be important factors contributing to variation in sperm producing ability of boars. Differences in mature testicular structure were evaluated in three breeds of boars known to differ dramatically in number of spermatozoa per ejaculate. At 5 to 7 months after puberty, White crossbred (WC) boars had larger testes (498 +/- 35g) than did Meishan (M; 247 +/- 17g) and West African (WA; 133 +/- 10g) boars, but the testes of WC boars (29 +/- 3 million/g) and WA boars (37 +/- 3 million/g) had a significantly greater number of Sertoli cells per gram of testes than did M boars (16 +/- 1 x 10 million/g). However, boars in all three breeds exhibited a similar rate of sperm production per gram of testis. Since spermatogenesis (transformation of germ cells into functional spermatozoa) occurs within Sertoli cells of the testis, the Sertoli cells in M boars were more efficient at producing spermatozoa than were the Sertoli cells in WC and WA boars. Enumeration of germ cells throughout stages of spermatogenesis confirmed that the Sertoli cells of M boars supported substantially more germ cells/Sertoli cell (39 +/- 5) than did Sertoli cells in WC (20 +/- 2) or WA boars (16 +/- 2). Further studies are necessary to elucidate the mechanisms by which Sertoli cells in M boars achieve this marked increase in efficiency of sperm production.
Technical Abstract: The objective of this study was to determine the number of Sertoli cells/boar, daily sperm production (DSP), and germ cell yield/type A spermatogonium in mature Whitecross (WC), Meishan (M), and West African (WA) boars. The paired parenchymal weight was greatest in the WC and greater in the M than WA. Total daily sperm production/boar (DSP, billions) differed significantly (p<0.05) among breeds (WC; 12.5+/-1.5; M: 6.0+/-0.5; WA: 2.9+/-0.3). DSP/boar was positively (p<0.01) correlated with parenchymal weight (r=0.97), number of A spermatogonia/testis (r=0.88), and Sertoli cell/testis (r=0.87). However, DSP/g was similar among all three breeds. Sertoli cell number/boar and number of type A spermatogonia/boar were greater for the WC but similar in the M and WA. Surprisingly, the number of Stage VII germ cells/Sertoli cell was much greater (p<0.05) in the M (39.08+/-5.07) than in the WC (19.91+/-1.62) and WA (15.81+/-2.43). The number of type A spermatogonia/testis was correlated (p<0.01) with Sertoli cell number/testis (r=0.95), and parenchymal weight (r=0.88). Spermatid yield per type A spermatogonium was greater in the M, and this ratio was positively correlated with spermatid:Sertoli cell ratio (r=0.62). Germ cell degeneration was similar (p>0.05) across breeds during spermiogenesis and averaged 8.6%. The increased number of type A spermatogonia and number of Sertoli cells associated with larger testes for the WC over WA or M boars is sufficient to explain the higher sperm production in the WC. However, a markedly lower index of spermatogenic degeneration and more efficient Sertoli cell function was present in M boars.