Keel bone damage is a well-documented issue affecting egg laying hens and the egg industry. Previous studies have indicated that keel bone damage has a physical effect on the birds likely through increased pain, but also increased mortality. Additionally, it creates an economic impact on the industry through reduced egg production and egg quality. Previous research has been conducted on keel bone damage, but it focused mainly on aviary and floor housing systems leaving the need to study enriched colony systems. This is an important distinction because the other systems provide more vertical space for bird movement which could affect the risk of keel injury.
The objective of this study was to evaluate the causes of keel bone damage (fractures and deviations) in laying hens that are housed in enriched colony cages. Impacts experienced at the hen’s keels were monitored as hens navigated their environments. The researchers then identified the forces associated with the impacts, and the specific behaviors and risk factors within the housing system that led to the impacts. The contributions of the identified risk factors to keel bone damage were evaluated against changes in keel bone damage status recording during the study.
There was an increase in the percentage of bones with at least one type of damage (factures and/or deviations) during each of the two three-week data collection periods conducted during this project. The study found a correlation between the number of collisions and the occurrence of new fractures and damages. Collisions occurred with perches and accounted for 74% of the total collisions recorded during the study. Other collisions occurred between the laying hen and the floor, other birds, metal equipment supports, feeders and cage walls. In some cases, collision causes were able to be quantified, these included movement from the floor to the perch, being pushed into an object, falling into an object and moving between perches.
This study was the first to report the energy thresholds of keel impacts by hens in enriched colony housing. Even though a definition of “high energy” impacts could not be definitively determined, the baseline for a preliminary definition was achieved and will aide future research. It was clear that perches were the primary source of “high energy” impacts and that while forces under 20 G can be classified as typical bird movement (i.e. wings), some hens experienced impacts at the keel with peak combined accelerations of over 100 G.
More data needs to be collected to determine the specific perch aspects that could be associated with the risk of keel damage. These may be height, design, location, etc. Other factors needing investigated are the roles of things outside of the scope of this study including things like genetics, housing types, etc.
The scientist who completed this work was Dr. Maja M. Makagon-Stuart, department of animal science at University of California - Davis. Dr. Makagon’s presentation at the 2017 Egg Industry Issues Forum regarding this research is available here.