Haematological reference intervals for pregnant Icelandic mares on pasture

Few studies have been conducted on haematological reference intervals (RIs) in Icelandic horses. Reference intervals have been published for Icelandic horses in Austria and a preliminary study in Iceland compared haematological values in riding horses to published RIs for other breeds as well as Icelandic horses abroad. Haematological parameters can vary greatly due to factors such as breed, gender, age, reproductive status, and training, as well as feeding, prior exercise and management method. Icelandic broodmares are kept on pasture under supervision throughout the year, with haylage provided during the winter, and it is therefore of interest to establish haematological reference intervals for pregnant broodmares in Iceland. The purpose of this study was to establish haematological RIs specific to Icelandic broodmares in the first months of pregnancy, kept on pasture. Blood samples from 183 mares, stabilised in EDTA were analysed using IDEXX ProCyte Dx and total protein was analysed in serum samples from 157 of the 183 mares, using IDEXX Catalyst One analyser. The RIs were established using the guidelines of the American Society for Veterinary Clinical Pathology.

The RIs for red blood cell count, haematocrit and haemoglobin were higher in pasture-kept Icelandic mares in early pregnancy, most of which were lactating, than in pregnant mares of other breeds. This was also true for white blood cell count, as well as numbers of monocytes, eosinophils, and basophils, which in some instances might illustrate problems in the automated categorisation of some leukocytes.

As no RIs have been published for other pasture-kept Icelandic horses, future investigations should include other groups of pasture-kept Icelandic horses. Such an analysis might elucidate the effect of breed, management, and pregnancy on haematological values in pasture-kept Icelandic horses.