Characterising and Managing Commercial Free-Range Laying Hen Sub-Populations

Abstract

<p>Free-range laying hens are perceived by consumers to live a more “natural” and “happier” life, with improved welfare compared to caged hens. However, the impact of free-range housing systems on bird health and welfare is poorly understood. Thus, the aim of this thesis was to provide evidence on how hens utilise the range and shed resources in an Australian free-range housing system, and examine the impact of this on bird health and behaviour. The research presented involved monitoring flock dynamics and measuring hen performance, with the aim of better understanding the nutrient requirements of free-range hens.</p> <p>In order to quantify individual hen usage of the range and aviary system, a Radio Frequency Identification (RFID) system was custom built by the University of New England to track 18 000 hens throughout the shed, both in the aviary system and on the outdoor range, in a commercial free-range farm. This RFID system technique was validated, achieving a precision of 90.0%, accuracy of 87.7% and specificity of 86.4%. The data produced allowed for individual hen’s occupancy at various zones to be determined, including duration of time spent at each of the four locations. Flock body weight was also assessed, as an indicator of bird health status. According to individual hen range use, flock sub-populations were identified and production performance and health of these sub-populations was investigated; these sub-populations were classified as ‘stayers’ and ‘rangers’, identified as hens that either spent the majority of their time in the shed or on the outdoor range, respectively. The results showed that these sub-populations clearly have different behaviours at different ages, impacting their mortality, health and welfare. Hens that were ‘rangers’ during early lay (18-21 weeks of age) were 3 times more likely to survive and had 10% higher egg production during early lay compared to hens that preferred to stay in the shed, but there was no difference on overall production over the life of the flock. The effect of range use on egg quality and bone health was also investigated, but no statistically significant effects were identified.</p> <p>In conclusion, this thesis demonstrates the successful application of modern tracking technology and machine learning to collect and utilise large data sets to accurately characterise behaviour, resource use, and resulting dynamics, of free-range hens. These methods provide powerful tools for evidence-based decision-making regarding housing design and management procedures, to achieve desired performance and welfare outcomes. One such advantage is that it may enable optimised use of feed resources to ensure the nutrient requirements of all sub-populations are achieved. </p>