The Effect of Repeated Blood Harvesting from Pregnant Mares on Haematological Variables.
Authors: Oddsdóttir Charlotta, Jónsdóttir Hanna Kristrún, Sturludóttir Erla, Vilanova Xavier Manteca
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Whilst the physiological impact of blood collection on non-pregnant horses is reasonably well established, pregnant mares—particularly those of hardy breeds managed extensively—present a distinct clinical scenario that has received limited scrutiny. Researchers at the University of Iceland monitored haematological responses in 160 pregnant Icelandic mares across two free-range herds, collecting weekly blood samples over multiple harvests and analysing erythropoietic markers and total serum protein to assess regenerative capacity during this metabolically demanding reproductive state. By the third collection, both herds demonstrated erythrocyte counts falling below minimum reference ranges, with up to 37% of animals presenting mild anaemia at peak; notably, one herd exhibited moderate to marked anaemia in 14.3% of individuals, though both groups mounted evidence of increased red cell production. All mares recovered to minimum normal haematocrit values within three weeks of cessation, suggesting inherent compensatory mechanisms, yet the divergent anaemic responses between herds—despite comparable management systems—points to unmeasured variables (nutrition, trace mineral status, individual genetics) that warrant investigation. For practitioners involved in breeding programmes or research protocols requiring serial blood sampling from pregnant mares, these findings underscore the importance of baseline haematological profiling and inter-herd monitoring, particularly where genetic or nutritional differences may compromise the margin between adaptive erythropoiesis and clinically significant anaemia.
Read the full abstract on PubMed
Practical Takeaways
- •Repeated weekly blood harvesting from pregnant mares carries significant risk of anaemia; monitor haematological variables closely if conducting serial collections
- •Recovery is possible within 3 weeks post-harvest, but regional and herd factors appear to influence susceptibility to anaemia—investigate management and nutritional differences between herds before implementing harvesting protocols
- •Limit blood harvesting frequency and volume in pregnant mares, particularly in herds showing suboptimal erythropoietic response
Key Findings
- •After three blood harvests, mares began showing erythrocyte numbers below minimum normal values, with mild anaemia present in up to 37% of animals
- •Moderate to marked anaemia developed in 14.3% of mares in one herd but not the other, indicating herd-specific variation in response
- •Both herds showed evidence of increased erythropoiesis in response to blood loss, but intensity of response differed between herds
- •All mares recovered to minimum normal haematocrit values within three weeks of the final harvest