Validation of Methods for Assessment of Dust Levels in Layer Barns.

The dust level is included in the animal welfare legislation of the European Union, implying assessment of dust levels during veterinary welfare inspections. This study aimed to develop a valid and feasible method for measuring dust levels in poultry barns. Dust levels were assessed in 11 layer barns using six methods: light scattering measurement, the dust sheet test with durations of 1 h and 2-3 h, respectively, visibility assessment, deposition assessment, and a tape test. As a reference, gravimetric measurements were obtained - a method known to be accurate but unsuitable for veterinary inspection. The dust sheet test 2-3 h showed the highest correlation with the reference method with the data points scattered closely around the regression line and the slope being highly significant ( p = 0.00003). In addition, the dust sheet test 2-3 h had the highest adjusted R 2 (0.9192) and the lowest RMSE (0.3553), indicating a high capability of predicting the true concentration value of dust in layer barns. Thus, the dust sheet test with a test duration of 2-3 h is a valid method for assessing dust levels. A major challenge is the test duration as 2-3 h is longer than most veterinary inspections. Nevertheless, results showed that potentially, with some modifications to the scoring scale, the dust sheet test may be reduced to 1 h without losing validity.