Garlic (Allium sativum) is claimed to have numerous beneficial properties to the health of humans and animals. It is commonly used for example to treat respiratory diseases and infections in horses' lungs. However, in addition to its possible positive influences, garlic may also have adverse health effects. The hypotheses of this study were that garlic supplementation may help to clear mucus in the airways, but also causes declining hematologic values in prolonged feeding. To our knowledge, this is the first organized study in controlled conditions to show the health effects of garlic supplementation for horses so far. The results show that long-term supplementation of dried garlic on the level of 32 mg/kg BW seemed to reduce the amount of tracheal symptoms and accumulation of tracheal exudates. Additionally, the number of neutrophil cells in the tracheal mucus was numerically smaller in the garlic supplemented horses. However, the garlic supplemented horses showed slightly declining Hb, HcT and RBC values during an 83-day study period. Consequently, it is possible that even low garlic supplementation levels can be detrimental to the horse's hematology when the supplementation period is long.
Keywords: dietary supplementation; hematology values; horse; nutrition; respiratory health.