Prevalence of twin foaling and blood chimaerism in purebred Spanish horses.

This study examines the occurrence of twin births and blood chimaerism, a condition where an individual possesses two different types of blood cells, in Spanish purebred horses. After examining over 21,000 horse births, the research found a very low rate of twin births and almost no chimaerism.

Overview of the Research

• The researchers conducted a study on twin births and blood chimaerism in purebred Spanish horses during the 2015-2016 breeding season.
• A total of 21,097 horse births were investigated to study the prevalence of these conditions.

Methodology

• The team analyzed foaling records and used short-tandem repeat (STR) parentage test results to identify twin births and any instances of chimaerism.
• An additional sex-linked STR-based technique was also employed in this study.

Results

• The study found only 14 twin pregnancies among the 21,097 births, resulting in 23 twin foals born alive. This represents a twin foaling prevalence of just 0.066%.
• Statistically, this suggests that instances of twin births in horses are extremely rare.
• Moreover, they found only five cases of blood chimaerism among the twin foals, giving an overall prevalence of 0.011%, indicating that chimaerism is extremely low in horses.
• Notably, the researchers did not find any true chimaeras (individuals with two different sets of DNA) in the study population.

Significance

• This research is considered groundbreaking as it is the first large-scale study looking into the occurrence of chimaerism in a horse population, and the first assessment of twin foaling in Spanish horses.
• These findings could have implications for future breeding and veterinary practices, as twin pregnancies can pose health risks for both the mare and her foals, and chimaerism can pose a challenge for genetic analysis and breeding strategies.