The focus of the 2012 International Society for Applied Ethology meeting in Vienna, Austria, was on Quality of Life in Designed Environments. While this is a multispecies conference, much of the research presented studied laying hens in a variety of housing systems. A concentration of papers was presented on feather pecking and management strategies to help minimize aggressive feather pecking in hens in alternative housing.
Dark brooders and feather pecking
Feather-pecking patterns can start at an early age. A report from researchers at Bristol University (Gilani et al.) indicated “dark brooder” rearing of pullets could reduce the incidence of severe feather pecking by tenfold. Dark brooders provide chicks a place to escape light and to rest undisturbed. It is basically a low-hung large box with black curtains on the side that chicks can get under to escape aggressive birds. Non-beak-trimmed pullet chicks were used in this trial. The benefits of dark brooders were persistent into lay, showing reduced feather pecking in layers, likely due to blocking the establishment of severe pecking habits early on.
Lambton, et al., Bristol University, investigated on-farm management strategies to reduce injurious pecking and reported reduced gentle feather pecking where nest boxes were not lit and litter quality was improved by scattering grit/grain. Severe feather pecking incidences were reduced when range was employed and when “breeze blocks” were provided along with high perch heights. Breeze blocks are bricks composed of cellulose material.
Flock size impact
Group size in enriched cage systems may also affect incidence of feather pecking according to research presented by Bilcik, et al., Slovak Academy of Sciences, Slovakia. They housed either five or 10 hens per 7,500 square centimeter enriched cage. They reported that groups of five hens displayed higher frequency of aggressive pecking and severe feather pecking compared to the 10-hen groups, which spent more time eating and standing. They concluded that contrary to expectations, some of the physiological and behavioral parameters at lower stocking densities were worse than for hens kept at higher density.
One research group went so far as to investigate the possibility of feeding chopped feathers to hens to reduce their appetite for feathers (Kriegsies, University of Hohenheim, Germany). They compared 5 or 10 percent chopped feathers or cellulose added to standard pelleted diets for a period of 16-17 weeks in two feeding trials. The addition of 5 percent feathers or cellulose did not reduce feather pecking or improve plumage condition; however, feeding 10 percent chopped feathers reduced severe feather pecking bouts and improved the plumage condition of the hens’ backs. The researchers concluded that the relationship between feather eating and the consequences thereof that alter feather pecking is unclear. These results give us some food for thought.
Epigenetics and behavior
There were also several very interesting symposia papers presented on the role of genes, epigenetics and environment on behavioral development. Epigenetics is the study of environmental effects on gene expression and modifications. Bas Rodenburg from Wageningen University, the Netherlands, described how epigenetic processes can change gene function without a change in gene sequence.
Stress in the parent or grandparent can translate to behavior and physical changes in the offspring. An example of this was the study of the genetic profile of laying hens in the presence or absence of maternal care. Maternal care results in adult hens that are less fearful with less aggressive behavior such as feather pecking.
A mutation in one of the receptor genes of the serotonergic system (HTR2C) was detected and associated with feather damage. This mutation was present in 84 percent of the single-comb white leghorn lines but only in 35 percent of the brown lines.
A favorable environment, during both ontogeny and later in life, plays a central role in behavioral development of laying hens. Dr. Per Jensen, Linköping University, Sweden, presented data supporting the role of stress in altering the expression of genes by means of deoxyribonucleic acid methylation. He measured DNA methylation in single-comb white leghorns versus Red Junglefowl for eight generations and found hypermethylation to be heritable and present in 79 percent of the genes in single-comb white leghorns, indicating many novel methylations during domestication. Jensen suggested that epigenetic mechanisms mediate stress effects on behavior and welfare in a heritable and adaptive manner. In short, environmental effects can cause long-lasting modifications in expression of the genome.
It will be interesting to follow the epigenetics discussion among geneticists as the environmental stressors change due to new laying hen rearing and housing systems. While some behaviors may become less severe in colony and aviary systems, others may become more of a problem.