Haematological responses of repeated large volume blood collection in the horse.

The haematological response of regular, repeated blood harvesting was investigated in 40 Thoroughbred and non-Thoroughbred horses that donate 8 litres of blood every 3 weeks for the purposes of commercial blood production. When this volume of blood was removed on five occasions over 12 weeks, no adverse effect on packed cell volume (PCV), haemoglobin (HB), and red blood cell count (RCC) was observed. Although PCV, RCC and Hb values decreased during the first week after blood collection, followed by a gradual increase in values until the next harvest time, all values remained within published reference ranges. Derived red cell indices [mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC)] also remained within reference range. We conclude that the removal of approximately 8 litres of blood (approximately 16 ml kg(-1)or 20 per cent of blood volume for a 500 kg horse) from blood donor horses every 3 weeks allows time for adequate recovery of haematological variables and does not result in adverse haematological changes.