Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/1998
Publication Date: N/A
Citation: Interpretive Summary: The use of artificial insemination by swine producers in the U.S. is increasing rapidly. Previously, we documented that daily sperm production is correlated positively to testicular size, and in the present study we investigated testicular composition of boars within sire families that differed in testicular size. We determined that number and size of Leydig cells and volume of the interstitium is similar in these two groups of boars that differed greatly in testicular size (315 vs. 525 g). The seminiferous tubules of these two groups of boars differ greatly in length (1.74 vs 3.71 m) and volume (211 vs. 401 cc) but not in diameter. Thus, the 44% lower total daily sperm production in boars with small testes was associated with 53% less seminiferous tubules. To improve total daily sperm production in boars, subsequent research must examine development of the seminiferous tubules and identify indicators of testicular size that can be evaluated early in life.
Technical Abstract: The objective of this study was to evaluate morphological characteristics and testicular function of boars with different endogenous concentrations of FSH. Boars were selected at 6 months of age on the basis mean FSH concentrations in plasma collected at 4, 5 and 6 months of age. Boars were classified within half-sib families based on whether they had high FSH (HiFSH, > 500 ng/ml, n = 9) or low concentrations of FSH (LoFSH, <500 ng/ml, n = 7). At 14.5 months, testes were collected, fixed, sectioned at 1 um and evaluated for morphological characteristics. Boars with LoFSH had larger (P < 0.01) testicular and epididymal weights than boars with HiFSH, greater (P < 0.01) daily sperm production per gram of testis and total daily sperm production per boar. Testes of boars with LoFSH had a greater (P < 0.03) percentage of seminiferous tubules (77% vs. 66%), a lesser percentage (P < 0.03) of Leydig cells (13 vs. 19%) and a somewhat lesser (P P= 0.06) percentage of vascular structures than testes of boars with HiFSH. Testes of boars with LoFSH had greater (P < 0.01) total tubule volume and tubule length (401 vs. 211 cc and 4181 vs. 1738 m) than testes of boars with HiFSH. There were no differences (P > 0.70) in volume, diameter or total number of Leydig cells, as well as total interstitial volume in testes (P > 0.41) of these two groups. Production of testosterone in vitro per paired testis (211 vs. 271 mg/hr) and per million Leydig cells (6.4 vs 8.4 ng/hr) was not different (P > .65) among boars with HiFSH or LoFSH. Greater concentrations of FSH in blood plasma were negatively associated with development of seminiferous tubules and spermatogenic efficiency; whereas Leydig cell development was not different in boars of these two groups.