The effects of cage design on bird welfare were presented at the International Society of Applied Ethology's annual meeting in Indianapolis between July 31 and August 4. This is the second time I have attended the meeting and presented research results, and perhaps the most significant impression I come away with each time is the diversity of worldwide perspective toward research regarding the care and welfare of poultry.
Effects of cage design
Starting with a U.S. study presented by authors from the University of California, Davis, Purdue University, Washington State University and Mississippi State University; Dr. Joseph Garner presented an epidemiological study on the effects of cage design on mortality in White Leghorn hens. This was a cross-sectional survey combining on-farm measurements and production records from 167 commercial laying hen houses. Results of the survey showed lower mortality in A-frame versus vertical cages, at an optimum floor space of 70 square inches per hen, in deep versus shallow cages, as feeder space per hen increased, with the use of nipple drinkers, in the W-36 strain of Leghorn hens, with evaporative cooling, with lower caloric intake, at lower light intensities and in flocks with cleaner feathers. The authors summarized that there are several risk factors for mortality associated with cage design, genetics, environment and diet.
In our research at the University of Nebraska, we compared feather loss in solid-sided cages to wire-sided cages over time in a flock of White Leghorn hens, and we tested dietary zinc supplementation as a preventative for feather loss. Our results showed no effects of zinc supplementation on feather loss, but did show significantly less feather loss in solid-sided cages compared to wire-sided cages, which further resulted in positive effects on hen body weight gain and quality of eggs produced.
Research conducted jointly between the University of Melbourne in Australia and Wageningen University in the Netherlands looked at the effects of enriched cage design on consistency of orientation and location during oviposition of laying hens. They studied floor space allowance and nest box access effects with Brown Leghorns. When hens were given more space, they had less variation in their timing of oviposition, likely due to less interference because of crowding during the sitting phase of oviposition, according to the authors. Hens with access to a nest box were also more consistent in site and orientation of oviposition. The authors conclude that the affect of housing design on egg laying behavior requires further research, as there is little data available on the effects of stress on consistency of egg laying behavior.
The University of California, Davis group (Alvino, Archer and Mench) presented a paper on Astroturf as a dust bathing substrate for laying hens. They conducted their research with White Leghorn hens in furnished cages containing an Astroturf pad that is often sprinkled with feed to promote dust bathing. The objective of the trial was to evaluate dust bathing in cages with Astroturf with or without feed, and a control with a sand dust bathing substrate. It was also noted if birds tried to dust bathe on the wire cage floor.
During the first trial they reported fewer dust bathing bouts on sand and on the wire floor compared to Astroturf with or without feed during the first period of study. Hens in sand also spent less time dust bathing on wire and more time dust bathing on substrates. After the initial trial, the dust bathing substrates were switched so that birds that had been in cages with Astroturf mats now had sandboxes and controls had Astroturf, and so on. At the end of the three trials, each group of birds had Astroturf for one trial, a sandbox for another trial, and neither a sandbox or Astroturf for one trial. During the second and third trials, there were no differences in time of hens spent dust bathing. The findings suggest that Astroturf might not be an adequate dust bathing substrate even with feed, and that exposure to Astroturf may even be aversive to hens as the proportion of dust bathing bouts in sand decreased after exposure to Astroturf.
A group of scientists from the University of Ghent in Belgium looked at remedies for the high incidence of broken eggs in some furnished cages: effectiveness of increasing nest attractiveness and lowering perch height. They reported that nesting material (artificial turf vs. plastic wire mesh) influenced the location of egg cracks, but not the percent of eggs broken or laid outside the nest. Cages with low perches (7 centimeters high) had a lower incidence of total eggs broken and laid outside the nest box compared to cages with high perches (24 centimeters). Lower perches seem to be a promising remedy for decreasing the high incidence of broken eggs in furnished cages, more so than the provision of Astroturf as a nesting material. These authors also reported observations on their videotapes of hens actually dropping/laying their eggs from the perches when next boxes are occupied continuously by a “boss” hen.
After listening to these presentations, I have several thoughts for us to ponder. The first is: Are the furnished cage designs available in today’s marketplace reflective of the most current research findings? Can nest box space be improved to provide more access for the timid hen and less breakage of eggs laid from perches? I feel that research efforts regarding design and welfare questions surrounding laying hen production are still in their infancy, especially in the U.S. Future research efforts such as the LayWel project in Europe and efforts of the Northeast Regional Poultry Research multi-state project NE-1042 “Optimization of Poultry Welfare and Production Systems for the 21st Century,” should help find answers for these important questions as our egg industry faces new challenges related to their production systems.