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Title: GROWTH OF TESTES AND TESTICULAR MORPHOLOGY AFTER EIGHT GENERATIONS OF SELECTION FOR INCREASED PREDICTED WEIGHT OF TESTES AT 150 DAYS OF AGE IN BOARS

Author
item HARDER, R - UNIVERSITY OF NEBRASKA
item Lunstra, Donald
item JOHNSON, RODGER - UNIVERSITY OF NEBRASKA

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fertility and sperm production of boars used for mating are important factors influencing reproductive efficiency in the swine industry, and testis size and earlier testicular development may be important factors affecting the sperm producing ability of boars. To better understand the genetic and biological mechanisms controlling testis size, a study was conducted to determine the effect of eight generations of selection for increased 150-day testis size in boars on testicular structure and onset of sperm production through 450-days of age. After eight generations, boars from the line selected for testis size (TS) exhibited greater testis weight and greater percentage of tubules exhibiting spermatogenesis by 70 to 160 days of age, compared to boars from a nonselected control line (C). Select line boars exhibited an earlier increase in testis mass and earlier appearance of spermatogenesis in tubules within the testis than did control lline boars. These results demonstrate that selection of boars for increased testis size at five months of age is effective, and that such selection results in earlier onset of puberty in the selected boars.

Technical Abstract: Weights of testes and epididymides, body weight, and morphometric measurements of testicular tissue of 75 boars of a line selected for eight generations for predicted weight of testes at 150 d of age and 75 boars of a randomly selected control line were used to evaluate the effects of selection on testicular development at 70, 100, 130, 160, and 450 d of age (n=15 boars per line per age). Body weights for boars of the select and control line did not differ (P<.05) and the shape of the body growth curve was similar for both lines. Boars of the select line had larger testes than control boars at each age (P<.05), but there was a significant line x age interaction. The percentage increase of the select line mean over the control mean for weight of testes was 37% at 70 d, a maximum of 120% at 100 d, and 25% at 450 d. The percentage of the testes made up of seminiferous tubules differed between lines (P<.01). Lines had similar means of approximately 28% at 70 d and 71% at 450 d, but the mean for the select line was larger between 100 and 160 d of age; the greatest difference was 11.6% (control = 43.7, select = 55.3%) at 100 d. After 70 d of age, select-line boars had a greater percentage of seminiferous tubules with lumens that contained elongated spermatids (P<.10). The proportion of the testes occupied by Leydig cells was greatest at 70 d, declined sharply between 70 and 130 d with a sharper decline in select-line boars, and then declined more gradually from 130 to 450 d of age. We conclude that selection for weight of testes at 150 d resulted in lower age at puberty for boars of the select line.