Our study showed that all chemical agents significantly
decreased the number of feathers plucked and eaten. The
2% and 4% quinine treatment eliminated feather plucking
and consumption completely, whereas the other treatments
had a lesser effect. In the current study we used high
feather-pecking birds selected on high feather-pecking
activity over 10 generations. It would be interesting to test
if the chemical agents used in this experiment would be
more successful in deterring hens from feather plucking,
when commercial breeds with a lower motivation to peck
at feathers would be tested.
Importantly, spraying feathers with an aversive agent
is amanagement tool which may raise concerns. The practice
ignores the underlying motivation of the birds and does
not address the decrease in the feather peckers welfare if
severe feather pecking has beneficial consequences for thepecker (e.g. gastro-intestinal benefits due to increasing gut
motility via ingested feathers). However, a recent epidemiological
study in the UK showed that 68.5% of laying hen
flocks at 25 weeks of age and 85.6% of laying hen flocks at 40
weeks of age showed severe feather pecking and plumage
damage (Lambton et al., 2010). The authors recommend
greatest weight should be given to improve environmental
rearing and laying conditions (e.g. beneficial and appropriate
foraging material) to decrease the problem of feather
pecking. However, when management attempts fail, spraying
with an aversive agent could be a solution during laying
(Harlander-Matauschek et al., 2010). So, aversive chemicals
are best considered a part of integrated strategies to reduce
severe feather pecking in problem flocks.
In practice, efforts to develop an aversive spraying solution
might focus on natural products or food additives
which are less toxic and environmentally safer, as the
development of such tools will be monitored by health,
food, veterinary and environmental agencies. However,
long-term and strong avoidance will come only from
such chemicals that produce adverse physiological effects
(chemicals acting internally may have the best chance).
Therefore efforts should be undertaken to develop spraying
devices, where the addition of cues could permit reduction
in the rate of harmful substances without losses in
effectiveness.