(E80) Fish Oil Supplementation Reduces Airway Neutrophilia in Thoroughbred Racehorses

Abstract: Background- When combined with low dust diets, omega-3 polyunsaturated fatty acids (O-3) supplementation can reduce neutrophil proportions in the bronchoalveolar lavage fluid (BAL) of horses with asthma and healthy horses. It is unknown if O-3 supplementation is effective without concurrent dust mitigation.
Hypothesis/Objectives- Dietary supplementation with fish oil rich in O-3 will lower the proportion of neutrophils in BAL of horses fed a conventional diet including hay.
Animals- Clinically healthy racing Thoroughbreds (55) housed at 4 US racetracks.
Methods- In this double-masked controlled trial, horses were randomly assigned to receive daily fish oil (50 ml) or placebo (corn oil) for 4 weeks. Exposures of particulate matter smaller than 10 µm (PM10) were measured and BAL was collected at baseline and after 4 weeks of supplementation. The effects of supplementation on BAL neutrophil proportions and the relationship with PM10 exposure were evaluated using a generalized linear model. Significance was set at p< 0.05.
Results- BAL neutrophils decreased from 7.8+/-0.01% to 5.3+/-0.01% (mean+/-s.e.m.) in horses given fish oil compared to placebo (5.9+/-0.01% to 9.3+/-0.02%; p=0.029). After 4 weeks of fish oil supplementation, PM10 exposure was not related to BAL neutrophils (p=0.2) but after placebo supplementation, PM10 exposure was related to BAL neutrophils (p< 0.0001), with a 10 µg/m3 increase in PM10 from the mean exposure resulting in a 1.3-fold increase in BAL neutrophils.
Conclusions and clinical importance- Supplementation with fish oil reduces BAL neutrophil proportions in clinically healthy racehorses independent of dust exposure. Increasing O-3 intake might help mitigate neutrophilic asthma in horses.