Outbreaks of severe feather pecking remains an onging challenge to the laying hen industry
Preventing and controlling outbreaks of severe feather pecking remains an ongoing challenge to the laying hen industry. Severe feather pecking involves pecking at and removing feathers causing bare areas of skin. This exposed skin increases the risk of further pecking leading to wounds, cannibalism, and mortality. Severe feather pecking is observed in anywhere from 8 to 65 percent of laying hen flocks. If it results in cannibalism, the mortality level can be very high. Research into why hens feather peck and how best to mitigate it has been ongoing for decades; however, the behavior remains unpredictable and difficult to control. Beak treatment is currently the most common and effective preventative measure against pecking-related injury; however, the practice is controversial. Beak treatment bans are already in place, or under consideration, by numerous countries in Europe and North America. This makes finding sustainable alternatives to beak treatment crucial.
Figure 1. Variation in beak shape observed between non-beak treated laying hen lines.
Recent research has suggested that genetic selection of the beak itself can be used as a tool to reduce injury from severe feather pecking and improve the chances of successfully housing non-beak treated laying hens. It was found that hens with blunter beaks had better feather cover and less mortality and that aspects of beak shape were heritable. Considerable variation in beak shape exists within and between non-beak treated laying hen flocks (Figure 1). This raises the question: can we take advantage of this pre-existing variation and genetically select hens whose beak shapes are less apt to cause injury? To answer this question, we first need to understand the range of variation for both the external beak and the bones that provide its structure.
Sarah Struthers, a PhD student at Scotland’s Rural College (SRUC) and the University of Edinburgh, is characterizing the pre-existing variation of the shape of the beak and its underlying bones that occurs within pedigree layer hen breeding flocks to investigate which beak shapes cause the least damage when hens engage in feather pecking behaviour. This work is a collaboration between SRUC, The Roslin Institute (University of Edinburgh), and Lohmann Breeders.
Her study, published last year in Poultry Science and winner of the 2022 Alltech Student Research Manuscript Award, is the first to examine the shape of the beak bones in laying hens. Using x-ray technology and geometric morphometrics (the analysis of shape using landmark coordinates rather than length/width/height measurements), the shape of the premaxillary (within top beak) and dentary (within bottom beak) bones were analyzed in two non-beak treated pure White Leghorn layer lines. The shapes of both bones differed significantly between the two genetic lines, suggesting that there are distinct bone shapes within each line. Line B hens tended to have shorter, wider premaxillary bones with a more pronounced downwards curvature than Line A hens (Figure 2). Line B hens also had dentary bones that were longer and wider than those of Line A hens. The size of both bones also differed between the two lines, suggesting that bone size may influence its shape.
In another study expected to be published next year, Struthers and her co-authors analyzed the shape of the external beak and its relationship to underlying bone shape. They found that the top beak had similar shape characteristics to the premaxillary bone and that the shapes of the beak and bone were moderately correlated. Overall, the distinct beak and bone shapes found within each genetic line suggest that there are specific beak shapes that could be selected for and the incorporation of shape data into breeding programs is possible.
As the final component of her PhD, Struthers is currently investigating if different beak shapes (in terms of curvature and length) cause different amounts of physical damage. Her trial, conducted at SRUC’s Allermuir Avian Innovation and Skills Centre, involved commercial laying hens pecking at “chicken” models – feathered chicken skin attached to foam blocks – and assessing the number of feathers removed and the damage caused to the blocks. This work is important as it helps lay the foundation for using the natural beak shape as a tool to reduce feather pecking damage in laying hen flocks.
Struthers’s PhD project funding comes from an SRUC Research Excellence Grant, the Flexible Talent Mobility Award scheme, and Lohmann Breeders.
Figure 2. Schematic showing the variation in premaxillary and dentary bone shape between Line A and B hens.
