The objective of this study was to determine effects of divergent selection for testosterone on testicular morphology and daily sperm production. Duroc boars from lines divergently selected for testosterone production in response to GnRH challenge for 10 generations followed by random selection were used. In generation 21 endogenous testosterone in the high testosterone line (H, n=54) and low testosterone line (L, n=44) averaged 490 ng/ml and 278 ng/ml (P < 0.01), respectively. Plasma FSH concentrations did not differ between lines (P < 0.3). Body weight, testicular weight, and epididymal weight were recorded for boars from H (n=82) and L (n=44) castrated at an average age of 211 d and 97 kg. Testicular tissues were sampled from animals castrated in generation 20 (H, n=46 and L, n=13). Volume densities for Leydig cells, seminiferous tubules, and Sertoli cells were estimated along with sperm production. After adjustment for body weight, average paired testicular weights for H and L were 417 g and 457 g (P < 0.01), respectively. Adjusted epididymal weights also differed between lines (P < 0.02), with H having larger epididymal weights. Line H (n=46) had greater volume densities of Leydig cells than L (n=13) (P < 0.02). Volume density of seminiferous tubules tended to differ between lines (P < 0.07), and Sertoli cell volume densities did not differ (P < 0.27). Sperm production traits, adjusted for age, did not significantly differ between lines. Selection for testosterone production in response to a GnRH challenge was an effective method of changing testosterone levels, testicular size, epididymal weight, and volume density of Leydig cells and seminiferous tubules. However, daily sperm production per gram of testes was unchanged. At this time, selection for testosterone in order to increase sperm production is not recommended.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-04092003-115030 |
| Date | 09 April 2003 |
| Creators | Walker, Sara Elizabeth |
| Contributors | Dr. O.W. Robison, Dr. William Flowers, Dr. Charlotte Farin, Dr. Joseph Cassady |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-04092003-115030/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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