Bone marrow response to large volume blood collection in the horse.

This study investigates how horse bone marrow responds to a large quantity of blood removal, using a method of progressively examining the bone marrow over a four-week period. The findings suggest that the production of new blood cells happens more slowly than previously understood.

Research Objective

• The primary aim of this research was to study the regenerative ability of the bone marrow in horses, specifically its ability to produce new blood cells (erythroid cells), following the removal of a large volume of blood.

Research Method

• For the study, a quantity of blood equivalent to 20 milliliters per kilogram of body weight was removed from five horses.
• Sequential bone marrow aspirates, or samples, were subsequently taken from these horses over a four-week period. These samples were taken from the sternum, or chest bone, of the horses.

Findings

• The researchers found that the total count of the erythroid cells (expressed as a percentage of the total number of erythroid and myeloid cells counted) initially increased by 13.7% within 3 days after blood removal.
• This erythroid response peaked by 9 days with a further 13.5% increase. This peak coincided with the lowest M:E ratio, indicating an increase in erythroid cells relative to myeloid cells.
• There was also a shift observed from proliferative phase cells to maturing phase cells, a shift that appeared to persist beyond 31 days post blood collection.

Conclusion

• The research team concluded that bone marrow in horses responded with a regenerative erythropoietic response more slowly than previously believed.
• They also highlighted that regeneration of the erythroid compartment was still not complete even 31 days after removal of a substantial volume of blood in the tested horses.