Livestock
Beef quality
Pre-slaughter stress reduces meat tenderness
Extensive evidence shows stressed cattle produce tough carcasses. New research by Department of Primary Industries
Victoria scientist Robyn Warner, Bruce Knee, from the Pastoral and Veterinary Institute, Victoria, and CSIRO Livestock
Industries scientist Drewe Ferguson highlights the importance of careful cattle handling pre-slaughter.
by
Industries Victoria, was to investigate the
effects of acute pre-slaughter stress in beef
cattle on beef eating quality.
The project followed earlier CRC work
which studied the impacts of mixing
unfamiliar cattle before slaughter and shorter
pre-slaughter lairage periods.
About 83 feedlot cattle destined for
the domestic trade were used on three
slaughter days.
On each slaughter day, a mob of cattle was
split and randomly allocated to a no stress or
stress treatment.
At 15 minutes pre-slaughter, the cattle in
the stress treatment were penned in groups
of four and individually given 6–8 electric
prods over 10 minutes with about one
prod per minute.
Cattle in the no stress treatment were kept
in isolation from the cattle undergoing the
stress treatment.
Robyn Warner,
DEPARTMENT OF PRIMARY
INDUSTRIES, VICTORIA
and Drewe Ferguson,
CSIRO
G
entle handling of cattle just before
slaughter can make a significant
difference to the eating quality of the meat.
A Co-operative Research Centre (CRC) for
Cattle and Beef Quality project has found
the treatment of animals during lairage,
when they are held at the abattoir before
slaughter, can have a large impact on stress
and the ultimate consumer acceptability of
the meat.
The new research shows that use of electric
cattle prods just before slaughter can cause a
significant decrease in eating quality and
water holding properties of meat.
A Meat Standards Australia (MSA)
consumer panel found meat from stressed
cattle was tough and less palatable than meat
from unstressed animals.
Pre-slaughter stress
Extensive research shows cattle exposed to
stressors between farm and slaughter (such
as transport, time off feed, exposure to
unfamiliar environments and handling) can
produce carcasses with the quality defect
known as dark-cutting, high pH beef meat.
Dark-cutting beef is caused by reduced
muscle glycogen and aside from the dark
colour of the meat, it can also have reduced
eating quality (for example, bland flavour,
variable tenderness) and a reduced shelf life.
For these reasons, dark cutting meat is
excluded from the MSA grading system.
Cattle undergoing acute stress in the
pre-slaughter period from the lairage
pen to the knocking box also could be
at risk of producing carcasses with reduced
meat quality.
Although less research has been carried
out in this area, acute stress pre-slaughter
could alter the post-mortem pH and change
the beef carcass response to electrical
stimulation.
Electrical stimulation of beef carcasses
is used in the MSA grading system to
ensure carcasses are within the optimum
post-mortem pH and temperature range for
desirable eating quality.
If electrical stimulation is applied to a beef
carcass that has undergone acute stress
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Consumer panels found meat from stressed cattle
was tough and less palatable than meat from
unstressed animals.
pre-slaughter, the resulting rate of pH fall
could be so rapid that the muscle proteins
change and produce pale, watery beef.
Pale, watery beef has a reduced ability to
tenderise as it ages and has high water losses,
potentially compromising the juiciness of the
beef product.
Stress treatment trial
The aim of the CRC trial, led by Robyn
Warner, from the Department of Primary
At a glance
• New Co-operative Research Centre
for Cattle and Beef Quality research
shows the treatment of cattle just
before slaughter can have a
significant impact on stress and the
eating quality of the meat.
• The results showed that the use of
electric cattle prods just before
slaughter could reduce meat
tenderness, juiciness and flavour.
• Future research will investigate the
mechanisms responsible for the
reduced eating quality of beef from
stressed animals.
Reduced meat quality
Cattle in the stress treatment demonstrated
evidence of an acute stress response,
as indicated by higher plasma lactate levels
at slaughter.
Lactate is produced during the breakdown
of muscle glycogen. The increase in the
plasma levels reflects increased glycogen use
in the muscles of the animals exposed to
the stress.
The water-holding capacity of the muscle
was reduced by the stress treatment, which
can lead to a loss in meat juiciness.
But the post-slaughter pH and temperature
decline of the Longissimus muscle or striploin
was not different between treatments.
Although there was no evidence for
an effect on pH or temperature, cattle
subjected to 6–8 electric prods in the last 15
minutes showed clear evidence of reduced
acceptability of the loin muscle to consumers
in terms of eating quality.
The MSA consumer panel found the
meat from stressed animals less tender and
juicy with a less acceptable flavour.
The acceptance score and meat quality
score were lower compared with meat from
cattle not subjected to stress (see Table 1).
Future research
The effect of stress on eating quality does
not seem to be directly linked to known
mechanisms associated with toughness.
It appears there could be other biochemical
factors affecting eating quality. Further
research is under way using new methods for
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No. 144
January 2004
Beef quality
Livestock
TABLE 1 Effect of acute pre-slaughter stress on beef eating quality
Meat Standards Australia consumer
panel assessments
Treatment
No stress
Stress
Tenderness
59.5
55.1
Juiciness
56.9
53.5
Flavour
61.0
57.2
Liking
59.6
55.9
Meat quality
59.6
55.6
Star
3.26
3.14
Note: The Meat Standards Australia Panel assessed the striploin muscle after 21 days of ageing in
a vacuum pack. A higher value indicates a more favourable assessment by the consumer.
Source: The Co-operative Research Centre for Cattle and Beef Quality.
measuring free radicals in muscle and blood
plasma, which could explain the mechanisms
for the reduced tenderness, juiciness and
flavour. The reason for targeting free radicals
is because of a recent experiment in sheep.
The trial showed that inhibition of an
enzyme in the muscle cell, known as
nitric oxide synthase, in the immediate
pre-slaughter period had an effect on loin
muscle tenderness.
Careful cattle handling
The results indicate that the beef industry
may have underestimated the impact that
even mild levels of pre-slaughter stress on the
animal can have on meat toughness.
Researchers estimate that between 5–20
per cent of cattle entering an abattoir
would exhibit symptoms of acute stress
pre-slaughter, potentially causing reduced
eating quality and consumer acceptability.
Currently, under the MSA systems, these
cattle would not be identified.
Producers are encouraged to take greater
care in the treatment and handling of animals
between the farm and abattoir.
The research also highlights the need
for processors to take more care in their
pre-slaughter management. The CRC is
putting together an information package
for the beef industry, which will cover the
New Co-operative Research Centre for Cattle and
Beef Quality research shows the use of electric
cattle prods in the last 15 minutes before slaughter
can have a significant effect on the animal’s stress
levels, resulting in reduced the eating quality and
consumer acceptance of the beef.
outcomes and recommendations of the
pre-slaughter stress research.
Acknowledgement: The Co-operative Research
Centre for Cattle and Beef Quality.
For more information contact Robyn Warner,
Department of Primary Industries, Victoria, by
email on [email protected] or
phone (03) 9742 0477 or Drewe
Ferguson, CSIRO Livestock Industries,
by email on [email protected],
or phone (02) 6776 1354.
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