Reference intervals for organically raised sheep: Effects of breed, location and season on hematological and biochemical parameters

Hematological and biochemical tests are widely used for assessment of health status and diagnosis of disease in domestic animals. They are almost indispensible in health management of organic flocks, but environmental conditions and food supply can be highly variable in organic farming, which may cause levels of many analytes to lie outside the published reference intervals. We investigated key hematological and biochemical parameters in organically raised sheep in Croatia. Different (mostly indigenous) breeds raised in various geographic regions were evaluated throughout the year. We identified key parameters that varied under different conditions using classification based on machine learning. Our findings suggest that location (which determines climate and food availability) has a profound effect on hematological and biochemical values in organically raised sheep. The effect of location was more pronounced than that of breed and season. The results clearly show the merit of establishing specific reference intervals for each flock, especially in organic farming. We demonstrate feasibility of this approach by successful calculation of reference intervals from a small sample (30 individuals) using robust statistical methods.