Sows that give birth to a high number of piglets often have piglets in the litter with lower birth weight, which are more likely to die after birth.
The high number of piglets is a result of the number of oocytes released (i.e. potential piglets), measured as the number of corpora lutea in the ovaries. Sows have on average 23 corpora lutea but give birth to approximately 16 piglets due to embryonic mortality.
This PhD-research shows that a high number of corpora lutea in the ovaries is not only related with a higher embryonic mortality, but also with less uniformity in weight and smaller placentae in live embryos, which might result in smaller piglets. Moreover, as the number of corpora lutea increases, their size decreases, and sows with smaller corpora lutea produce lighter piglets at birth. The relationship between corpora lutea size and piglet birth weight is partly genetic as gilts that had a higher genetic potential for piglet birth weight also had larger corpora lutea during pregnancy.
This research has increased our understanding of embryonic survival and development in sows that give birth to large litters. Especially the relations with corpora lutea size are of interest and may be used by breeding companies to improve piglet birth weight, which can decrease piglet mortality and increase profitability and animal welfare.