Agriculture Reference
In-Depth Information
be penned separately. Larger animals will usually be
aggressive to smaller ones. It is important to recognise,
however, that both are stressed. This can be seen espe-
cially in young bulls which, if mixed in the lairage, can
rapidly become exhausted through constant mounting.
Mixing of young bulls is therefore contraindicated, and
they should be slaughtered as soon as possible after
arrival in the lairage. It has been noted that if these ani-
mals remain in the lairage for only 2-3 hours, they may
produce dark-cutting meat.
The movement of sheep through a lairage may be
facilitated by the use of a decoy or 'Judas' sheep. This
procedure utilises the innate tendency of sheep to follow
one another by 'training' one particular sheep, or allow-
ing it to become accustomed, to pass through the lairage
leading the others. Use can be made of a mirror, strategi-
cally placed, to assist the movement of sheep out of a pen
(Franklin and Hutson, 1982). It is particularly important
when driving sheep to exercise patience and give them
time to move at their own pace. Attempts to rush will
result in those at the rear climbing over or riding on
those in front, resulting in bruising.
Pigs can be particularly awkward to drive. They move
only as a loose group, optimum group size 5 or 6, prefer-
ring to move along beside rather than behind their com-
rades. The maximum number of pigs which should be
moved as a group is 15. This is also considered to be the
ideal group size per pen at a stocking density of 0.55-
0.67 m
2
/100 kg. Lewis and McGlone (2007) demon-
strated that it took the same time to load 170 pigs in
groups of 5 or 6 compared with a group size of 10 but the
latter had elevated heart rates.
Excessive or strident
noise
can be very stressful to live-
stock, especially pigs. Measurements indicate that noise
levels average 75 dB in lairage pens, rising to 100 dB in
the pre-stunning pen. This may arise from human voices,
the use of whips, noisy machinery, barking dogs, com-
pressed-air brakes on vehicles, alarm bells, thunder, etc.
The manufacturers of meat plant equipment have a duty
to ensure that equipment operates as quietly as possible,
especially in the stunning area and its immediate sur-
roundings. The provision of rubber baffles on doors and
gates is essential.
Cattle are more sensitive to high-frequency sound
than are human beings. The auditory sensitivity of cattle
is at its greatest at 8000 Hz compared with 1000-3000 Hz
in man. Unusual and especially intermittent sounds are
upsetting to all classes of livestock. Sheep are visibly
frightened by the sight and barking of dogs.
Watering
The drinking water supply to pens should be designed to
allow all animals access to clean water at all times. This
simple principle can be obstructed if pens are over-
stocked so making it physically impossible for some ani-
mals to access the drinkers. Ample drinking water during
their retention in the lairage also serves to lower the bac-
terial load in the intestine and facilitates removal of the
hide or pelt during dressing of the carcase. Stunning of
animals by electrical means is rendered more efficacious
if they have received unlimited water during their deten-
tion prior to slaughter. The positioning and design of
water troughs or drinkers is of particular importance in
order that faecal contamination of the water is avoided.
Self-filling bowls are generally more satisfactory than
large concrete troughs for cattle, and drinkers recessed
into the walls of the pens are preferred for pigs. Water
nipples are not always readily used by pigs, and some
protrude from the pen wall at a height which renders
them a welfare hazard.
Fasting
Among butchers throughout the world, the practice of
withholding food from animals prior to slaughter has
long been observed, it being contended in support of this
practice that fasted animals bleed better, that the carcase
is easier to dress and that it has a brighter appearance.
Scientific evidence for such assertions is lacking and the
hungry animal does not settle as well as the animal that
has been fed. It is also a known physiological fact that
although cattle and sheep are better able to withstand
cold than pigs, resistance to the shock of a severe fall in
atmospheric temperature is greater in the fed animal
than in one that has been starved.
However, there is a duty to ensure that animals are not
presented for slaughter with full stomachs to prevent
carcase contamination due to accidental incision or
rupture of the gastrointestinal tract during the dressing
procedure. Guise
et al.
(1995) reported that stomachs
from pigs which had been fed 0.64 kg of dry matter and
slaughtered 18.5 hours later had on average a wet stom-
ach content of 0.87 kg (0.24-1.33). In recognition of
Social stress
Mixing strange animals together may make them fight to
establish a new social order; once this is achieved, fight-
ing ceases. This may occur during marketing, transport
or in the lairage. Work carried out by Moss and Trimble
(1988) in Northern Ireland showed that if cattle were
mixed and were active, and their muscle glycogen was
depleted, it took at least 2 days, in most cases 3, for this
to be replaced.
Aggressive animals and females in oestrus must be
isolated, as must horned from polled stock. Although
young bulls reared in groups as bull beef may be penned
together, breeding bulls and boars should always
