Agriculture Reference
In-Depth Information
the mean ultimate muscle pH was significantly higher
for the 28 hour group (0.34 pH units), but this effect was
much more apparent for bulls (0.60 pH units) than for
steers (0.27 pH units) or heifers (no change), presumably
owing to the greater activity that characterises the behav-
iour of bulls. On the basis of this work, it may be sug-
gested that in order to maximise carcase yield and meat
quality, holding of cattle in the lairage should be restricted
to 4 hours. The number of variables between lairages,
however, means that such a recommendation should be
treated with caution.
Warriss
et al.
(1992b) demonstrated that in pigs, blood
cortisol and beta-endorphin levels return to normal val-
ues after 2-3 hours in the lairage. These blood constitu-
ents measure mainly psychological stress and support
the observation that the majority of pigs, whether in sin-
gle or mixed producer lots, cease to fight after the first
hour in the lairage and settle down to rest (Moss, 1977).
A period of rest of 2-3 hours for pigs has therefore been
recommended. It allows sufficient time to recover from
previous stresses without significantly increasing the
problems of long food deprivation, muscle glycogen
depletion and skin blemish seen after longer periods,
particularly after holding overnight.
Excessively long periods of retention
only serve to make
the task of lairage cleaning - one of the most difficult
tasks in the meat plant - even more difficult, as well as
increasing the possibility of cross infection.
It has been
found, for example, that the longer pigs and calves are held
prior to slaughter, the greater is the build-up of infection,
particularly of Salmonella organisms, and the greater the
risk of cross infection
. In one experiment with calves
awaiting slaughter, it was shown that after a few hours'
detention, only 0.6% of the animals harboured salmonel-
lae, whereas after 2-5 days, 55.6% had
Salmonella
in
their intestine. Other authorities have recorded
Salmonella
in 7% of farm pigs, 25% of pigs in the lairage
pen and 50% of pigs at slaughter; 75% of lairage drinking
water was also infected. It is recommended, therefore,
that young calves be slaughtered as soon as possible after
arrival at an abattoir because of the risk of cross-contam-
ination and because it is difficult to induce calves to eat.
Small pens with solid bases to the partitions, given regu-
lar cleansing and disinfection, will considerably lower
the risk of cross infection with
Salmonella
organisms.
these arguments, EU Regulation 1099/2009 requires
animals which have not been slaughtered within 12
hours of arrival at the slaughterhouse to be fed and sub-
sequently to be given moderate amounts of food at
appropriate intervals.
Resting of animals prior to slaughter
The actual duration of the resting period necessary to
ensure normal physiological changes in the muscle after
slaughter depends on many factors. These include the
species, age, sex, class and condition, time of year, length
of journey, method of transportation, etc. Where differ-
ent species are handled within the one lairage, it is
important to ensure that proper arrangements are made
for movement forwards for slaughter after an adequate
resting period for the particular animals involved. Cows
in good condition in temperate countries should not be
held for long periods during winter because of the pos-
sibility of hypomagnesaemic tetany. Spring lambs require
a relatively shorter period of rest than adult sheep and
tend to lose weight with prolonged holding.
However, the quality of the rest encountered in the
lairage has been brought into question. Cockram (1991)
argues persuasively that the novel environment of the
lairage, with people moving around, may not provide
optimal conditions for cattle to rest, as measured by lying
behaviour. Although conditions may improve overnight,
with cattle lying down and resting, he suggests that the
evidence is unclear as to whether the meat quality from
cattle held overnight in the lairage shows a significant
improvement.
It has been determined in Australia that the ultimate
pH in steer carcases was lower in animals that had been
rested and fed for 4 days than in animals rested for only
2 days after a 320 km (200 mile) journey. In the same
country, the ultimate pH values in the carcases of rams
were higher, and the meat colour was darker in animals
rested for 120 hours after a journey by road of 1110 km
(690 miles). In Bulgaria, blood and muscle values in
calves transported by road for up to 450 km were back to
normal in 24 hours.
McNally and Warriss (1996) demonstrated that as the
time cattle were held in the lairage increased, the amount
of bruising increased significantly.
In New Zealand, Purchas (1992) investigated the
effect of decreasing the holding time in the lairage from
28 to 4 hours, after 2 hours' transport. Overall, the dress-
ing-out percentage based on full live weights was signifi-
cantly lower for the 28 hour group, so that for the mean
live weight of 483 kg, the extra 24 hours of holding time
led to 4.5 kg less carcase weight, with the rate of loss
being slightly greater for the heifers. Perhaps surpris-
ingly, if the lairage is to be considered as a place of rest,
Pre-slaughter handling and meat quality
Stress and the animal
During the process of loading at the farm, the journey to
the abattoir or market, the holding at the market, the off-
loading, the detention in the abattoir lairage and the sub-
sequent handling up to the point of slaughter, the animal
