Relationships between range characteristics, ranging behaviour, and welfare of commercial free-range laying hens

© 2017 Dr. Hannah LarsenLaying hens in free-range housing systems are often considered by consumers to live a more natural life, be happier, and have better welfare than hens in other housing systems, primarily due having access to an outdoor range. However, the behaviour and welfare of hens in commercial free-range housing systems is poorly understood. This thesis aimed to gain a better understanding of hen behaviour and welfare on commercial laying hen farms in Australia. Chapters 2 and 3 of this thesis examined hen behaviour in the outdoor range in relation to natural range features to gain an understanding of both preference for different range features, and daily behavioural time budgets. The results showed that hens displayed clear preference for some areas of the range over others depending on the environment, and that the most preferred area mimicked the dense forested natural habitat of their wild counterparts. Additionally, the areas that hens were most attracted to also allowed hens to perform a wider variety of behaviours throughout the day. Generally, the time budget of laying hens observed in these studies went from active behaviours in the morning and evening (foraging, walking), and resting behaviours during the middle of the day (preening, resting, perching). This suggests that the number of hens in the range could be increased by providing areas hens prefer, and hen distribution could be improved through range design. In Chapter 4, hens preference for artificial structures based on three principles of design (height, orientation, and visual density) was tested. Hen preference varied according to all principles with a three-way interaction. Hens preferred structures that had the greatest visual density, provided both overhead and vertical cover, and were lower to the ground. The behaviours hens performed around these structures also varied depending on the principle, however, the number of behaviours observed was fewer than seen in the first two studies. Artificial structures may have benefits over natural structures because they can be implemented quickly, may attract fewer wild birds, and can be easily moved in the range. In Chapters 5 and 6 of this thesis, individual hen use of the outdoor range on two commercial flocks was tracked using Radio Frequency Identification (RFID) technology. Furthermore, hen movements were also tracked across three outdoor zones at increasing distances from the shed: the veranda [0–2.4 m], close range [2.4–11.4 m], and far range [>11.4 m]. Chapter 5 describes the ranging behaviour of individual hens and found that the majority of hens in this study used the outdoor range every day of the study (68.6% in Flock A and 82.2% in Flock B), and most hens accessed all three zones of the range (73.7% in Flock A, and 84.5% in Flock B). The veranda zone was most popular, as hens spent half of their time outdoors in this area. Additionally, the consistency of which individual hens used the range in relation to duration and frequency varied considerably between hens. Chapter 6 assessed the relationship between the ranging behaviours and hen welfare. A variety of behavioural, physiological and health indicators of hen welfare were taken. Hens that ranged more were more fearful of humans, had higher basal stress levels, lower neophobia, darker combs, and better beak condition than hens that ranged less. Overall, relationships between ranging and welfare were relatively weak, suggesting that there is not a strong link between range use and hen welfare. This thesis demonstrated that the modern laying hen retains the preferences of their wild counterpart, suggesting that the outdoor range can be designed to both increase the number of hens using the range, and the distribution of hens within the range. In the commercial free-range flocks studied during this thesis, the majority of hens used the outdoor range on a regular basis. However, the relationship between range use and welfare observed in this study was weak. Hens in free-range housing systems are presumably able to choose whether they use the outdoor range and the nature of that use, thus an alternative hypothesis might be that hens in free-range systems are able to manage their own welfare needs via-free choice. Further research on the causal relationships between range use, the behaviours hens perform in the range, the nature of range use, and laying hen welfare is needed