Abstract
Low atmospheric pressure stunning (LAPS) is a new irreversible stunning method for broiler chickens (Gallus gallus domesticus),
which has the potential to improve welfare during routine slaughter.
During LAPS, birds are placed in a hypobaric chamber that allows oxygen
to be gradually removed from the environment by the controlled removal
of air; the staged process takes 280s and reaches final decompression
pressure that is 80.6 kPa below atmospheric pressure (nominally
101.3 kPa for an absolute vacuum pressure of 20.7 kPa). In this study,
the behaviour of broilers (50 individuals and 50 focal birds killed in
groups of 20) was observed during LAPS. Latencies, total durations,
single bout durations and number of bouts were recorded for all
behaviours. Three different decompression curves were applied during the
process (based on automatically applied settings related to ambient
temperature) and their effects on behaviour were investigated. Not all
birds displayed all behaviours, but a subset of behaviours (ataxia, loss
of posture, clonic and tonic convulsions and leg paddling) occurred in a
consistent sequence. In individuals, mandibulation, headshaking and
open bill breathing occurred earliest at 44.5 ± 31.6 s, 50.8 ± 38.3 s
and 57.4 ± 35.8 s, respectively, after LAPS began. Ataxia was observed
on average at 57.3 ± 11.5 s, with birds killed at colder temperatures
taking slightly longer to succumb to ataxia than those at warmer
temperatures. Loss of posture (LOP) is regarded as a behavioural marker
for loss of consciousness and it occurred on average at 80.7 ± 17.7 s.
Clonic and tonic convulsions were displayed after LOP at 110.5 ± 37.6 s
and 117.4 ± 28.8 s after LAPS onset, respectively. Mean time to
motionless was 199.4 ± 21.3 s. The group data were largely similar to
that of individuals but were less reliable due to focal birds being
obscured by neighbours. Based on LOP, the data suggest that birds are in
a conscious state for longer during LAPS than in controlled atmosphere
stunning with inert gases, but although the induction to unconsciousness
is more gradual, other behavioural responses were equivalent. The
occurrence of mandibulation, head shaking, and open bill breathing may
be an indication of reduced welfare or may be indications of a
non-painful physiological responses to hypoxia in a hypobaric
atmosphere. These behaviours occurred at similar levels as seen in CAS
with inert gases in poultry and the lack of escape behaviours as well as
absence of signs of severe dyspnoea suggest that LAPS is a humane
approach to stunning of poultry.
Original language | English |
---|---|
Pages (from-to) | 90-98 |
Number of pages | 9 |
Journal | Applied Animal Behaviour Science |
Volume | 174 |
Early online date | 26 Nov 2015 |
DOIs | |
Publication status | Published - Jan 2016 |
Keywords
- Animal welfare
- Hypobaric hypoxia
- Humane slaughter
- Loss of posture
- Low atmosphere pressure stunning