The assessment of litter quality in broiler chickens: validity, inter-assessor reliability, and intra-assessor repeatability of three visual scoring systems

1. This study evaluated the validity, inter-assessor reliability and intra-assessor repeatability of three visual scoring systems for litter quality, one known as the Welfare Quality Assessment Protocol (c) and two complementary systems for friability and humidity developed by the ClassyFarm initiative. 2. In 6 rooms of an experimental barn, 2450 medium-growing broiler chickens were reared on coarse sawdust litter until they reached a body weight of 2.2 kg at 43 days of age, with a stocking density of 33 kg/m(2). 3. Sixty-six litter samples were analysed for litter moisture at two different time points during the broiler chickens' production cycle, and were visually scored using the three systems, two consecutive times, by 7 assessors to analyse their validity, inter-reliability and intra-repeatability according to the litter moisture level. 4. The three resulting scores were correlated with the litter moisture (p < 0.001) and correlations were stronger when the litter moisture was above 35%. Similarly, inter-assessor reliability and intra-assessor repeatability were better for all three scoring systems when litter moisture was above 35% than when it was below 35%. 5. The ClassyFarm Friability system was the most reliable regardless of litter moisture level. The ClassyFarm Humidity system was the least reliable and repeatable when the litter moisture was below 35%. The Welfare Quality scoring system lay between the two ClassyFarm systems considering inter-assessor reliability, but was as repeatable as the ClassyFarm Friability system.