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Early embryonic development in prolific Meishan pigs
1Iowa State University, Ames 50011-3150.
Journal of Reproduction and Fertility. Supplement
|January 1, 1993
Summary
Chinese Meishan pigs have lower embryonic growth and estrogen secretion, potentially explaining their higher litter survival rates compared to European breeds. This difference is influenced by the uterine environment, not just the embryo itself.
Area of Science:
- Reproductive Biology
- Animal Science
- Genetics
Background:
- High prenatal mortality (30-40%) in European pigs, primarily post-day 12, impacts litter size.
- Chinese Meishan pigs exhibit greater prolificacy, with early theories suggesting lower embryonic mortality.
- Previous research indicates no breed differences in early embryo mortality (pre-day 12) or morphological diversity.
Purpose of the Study:
- To investigate the reasons behind the prolificacy of Meishan pigs compared to European breeds.
- To determine if reduced embryonic growth rates and estrogen secretion contribute to higher litter survival in Meishan pigs.
- To assess the role of the uterine environment in regulating embryonic development.
Main Methods:
- Comparison of preimplantation embryo growth rates and estrogen secretion between Meishan and Yorkshire (European) females through day 12.
- Assessment of conceptus size on day 30 of gestation in Meishan and European breeds.
- Cross-transfer experiments involving Meishan and Yorkshire embryos into Meishan and Yorkshire recipient uteri on day 2, with subsequent analysis on day 12.
Main Results:
- Meishan embryos exhibited significantly reduced growth rates and estrogen secretion by day 12 compared to Yorkshire embryos.
- Meishan conceptuses were significantly smaller on day 30 of gestation.
- Embryos (both Meishan and Yorkshire) transferred to Meishan uteri showed reduced morphological development and estrogen content on day 12 compared to those in Yorkshire uteri.
Conclusions:
- Reduced embryonic growth and estrogen production in Meishan pigs do not explain their prolificacy; rather, the uterine environment plays a crucial role.
- Factors within the Meishan uterine endometrium appear to reduce the growth rate and estrogen secretory potential of preimplantation conceptuses.
- These endometrial factors may lead to more gradual uterine environment changes, benefiting conceptus survival and contributing to larger litter sizes in Meishan pigs.