Space use of free-range laying hens on two outdoor ranges with different amounts of vegetation cover

Abstract

Consumers’ awareness of animal welfare in farm animal husbandry – including laying hen systems – increased in the last few decades. As a result, more and more farmers in Austria changed from barn systems to free-range husbandry. However, lack of structure and protective cover in the outdoor area might cause poor use of major parts of the outdoor range. Since the ancestor of domestic chicken – the red junglefowl – inhabits dense jungle forests with manifold ground vegetation, the structural design of an outdoor area might be of high importance for laying hens. To examine this assumption, a 15×15 m grid of barrier tape was brought out on the ground of the outdoor ranges of two commercial free-range laying hen farms that differed in the amount of vegetation cover they provided. Using action cams, we took pictures of each quadrant in ten-minute intervals from 09:00 h to 21:00 h for a total of three full days. We ran GAMs for each farm separately with number of hens per quadrant and interval as dependent variable, and vegetation cover (yes/no) and position (edge/centre) of the quadrant, distance to the shed (in m), as well as temperature (in °C) as predictors. Date, time, and quadrant ID were included as smooth terms. We found a more even and widespread use of space of hens on the outdoor range with a large amount of vegetation cover (farm 1) compared to the range with a small amount of vegetation cover (farm 2). However, the number of hens decreased with increasing distance to the shed on both farms. Hens preferred edge over centre quadrants on the range of farm 1, but preferred centred quadrants with vegetation cover over those without cover on the range of farm 2. On the ranges of both farms, the number of hens decreased with increasing temperature on quadrants without vegetation cover, whereas no such effect was found for covered quadrants. These findings suggest vegetation cover to be a key factor for extensive range use, particularly in view of the expected increase in temperature due to climate change. Therefore, we recommend farmers to provide hens with highly structured outdoor ranges, not only to improve range use but also to offer hens a more species-appropriate environment, which is assumed to increase the hens’ welfare as well.