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Realized heritability estimates in boars divergently selected for testosterone levels(1,) (2)
O W Robison1, D Lubritz, B Johnson
1Department of Animal Science North Carolina State University, Raleigh, USA.
Summary
Selection for higher testosterone levels in Duroc boars resulted in a three-fold increase in testosterone production after 10 generations. This selection also led to significant improvements in litter size and correlated effects on growth and carcass traits.
Area of Science:
- Animal Breeding and Genetics
- Reproductive Physiology
- Quantitative Genetics
Background:
- Testosterone plays a crucial role in male reproductive development and performance in livestock.
- Understanding the heritability of testosterone production is essential for genetic improvement programs.
- Previous research has explored genetic parameters for various production traits in swine.
Purpose of the Study:
- To estimate realized heritabilities for testosterone production in Duroc boars.
- To investigate correlated responses in growth, carcass, and reproductive traits due to selection for testosterone levels.
- To evaluate the effectiveness of selection for divergent testosterone levels over 10 generations.
Main Methods:
- Data collected from 100 sires and 891 Duroc boars over a 10-year period (1982-1992).
- Testosterone levels measured from peripheral blood samples before (PRE) and after (POST) Gonadotropin-Releasing Hormone (GnRH) challenge.
- Realized heritabilities estimated using regression of response on cumulative selection differentials; correlated responses analyzed for testes volume (TVOL), days to 104 kg (DAYS104), number born alive (NBA), and backfat (FAT).
Main Results:
- Realized heritability for POST testosterone was estimated at 0.24 ± 0.08 in the high line and 0.15 ± 0.18 in the low line.
- After 10 generations, the high selection line exhibited approximately three times greater PRE and POST testosterone levels compared to the low line.
- High line pigs showed a significant increase in number born alive (NBA) and a trend towards reduced days to 104 kg (DAYS104), increased backfat (FAT), and larger testes volume (TVOL).
Conclusions:
- Selection for testosterone levels is feasible and can lead to significant genetic gains in boars.
- Divergent selection for testosterone resulted in substantial increases in testosterone production and positively impacted reproductive traits like litter size.
- Correlated responses suggest potential for simultaneous improvement of reproductive efficiency and certain production/carcass traits through selection on testosterone.
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