Observations
at packing plants indicate that some lines of hybrid pigs have a very nervous
temperament and others are calm. Some pigs are easy to drive up chutes and
others are nervous and constantly balk and back up. Certain lines of lean pigs,
which contain the stress gene, tend to be more nervous and excitable than lean
lines without the stress gene. Observations at large packing plants have also
indicated that lines with some Duroc genetics tend to be calmer. Lines with
Hampshire or Pictrain genetics tend to be more nervous. Shea-Moore (1998) found
that a certain genetic line of high lean pigs were more fearful than fatter
types. She also found that they balked more during driving. Some genetic lines
of high lean pigs fight more than fatter pigs (Busse and Shea-Moore 1999). Some
producers have moved away from lines which are extremely nervous and carry the
stress gene. This also has the
added benefit of improving pork quality. Pork from heavy weight pigs with the stress gene was judged by a taste panel to be tougher and drier then normal pork (Monin et all 1999).
added benefit of improving pork quality. Pork from heavy weight pigs with the stress gene was judged by a taste panel to be tougher and drier then normal pork (Monin et all 1999).
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Problems associated with Ultra Heavy Muscling
There
are certain genetic lines of pigs that have extreme bulging hams. Some of these
pigs have difficulty walking and they are prone to back breakage during
electric stunning because the muscles grow so rapid¡y that the skeleton is
immature and small. The author has observed a much higher incidence of broken
legs in these pigs that occur during handling and loading. They also have
double to triple the problems with damaged meat, blood splash and broken bones
induced by electric stunning. In one plant, ultraheavy muscled pigs accounted
for 90% of the broken backs and severely damaged loins. Problems with weak
bones are further worsened if a producer fails to properly supplement the
finishing diet. Providing adequate minerals enables a pig to build stronger
bones. Finishing pigs at very high weights such as 300 to 350 pounds will also
increase death losses, broken bones and PSE. Lines with Hampshire or Pictrain
genetics tend to be more nervous. The author has also observed that pork from
ultra lean pigs with bulging muscles is often tough.
Behaviour of lean pig when walking
Practical
experience has shown that lean pigs with excitable genetics will be easier to
load into trucks and handle at the packing plant if the producers have walked
through the pens every day during finishing. This is especially important in a wean
to finish operation where the piglets remain in the same building from weaning
to finishing. Only 10 to 15 seconds per pen per day is required. In facilities
with large pens provide 10 to 15 seconds per 50 pigs, everyday. The principle
is to train the pigs to calmly get up and flow around the person. If the person
stands still as he/she trains the pigs to chew on boots instead of moving. It
is important to keep moving in the pens. The person should move at the same
speed as a pigs normal walking speed. The person walking the pens should also
walk through the pens in a different random direction each day. The handler's
goal is to teach the pigs to drive. One large pork operation with a high
percentage of pigs carrying the stress gene found that walking the pens greatly
reduced death losses during transport and in the plant yards.
Enriched Environment
Research
studies on the effects of environmental enrichment have had varying results
(Grandin 1987, 1989, Pedersen et al 1993). In some trials contact with people
made pigs easier to handle and in others it made them harder to drive. One of
the causes of negative results was spending too much time in the pens. This
caused the pigs to become too tame and refuse to drive. They wanted to follow
people instead of driving. Other studies showed that allowing pigs to walk in
the aisle every day made them easier to load onto a truck (Abbot et al 1997,
Geverink et al 1998).
In
studies where handling in the pens made pigs harder to drive, much more time
was spent interacting with the pigs than the 10 to 15 seconds per day which the
author recommends. There is an optimal level of exposure for people. An animal
needs to be tame enough not to panic but not to be so tame that it wants to
follow people instead of driving. The secret is actually training the pigs to
move calmly when the person walks through the pens. The handler must never kick
or slap the pigs. This would stress the pigs. Calm handling and walking through
the pens will have no effect on weight gain. To prevent any possible
detrimental effect, walking the pens should be done during the entire finishing
period. There may be detrimental effects if a producer attempts to walk the
pens for only one week prior to slaughter.
Moving and Loading Finishing Pigs
1.
When loading finishing
pigs, move very small groups of 5 to 6 at a time.
2.
Do not store large
groups of finishing pigs in an alley or holding pen. This will lead to damage
caused by fighting. It is best to take each small group of pigs immediately
from the finishing pen to the truck.
3.
New finishing buildings
should have a 3-foot (1 m) wide alley. This is wide enough to allow 2 pigs to
walk down it side by side. If a building has a 2-foot (.75 m) alley, only three
pigs should be moved at a time.
4.
Do not overload the
trucks. An overloaded truck, especially during hot weather, is a major cause of
high death losses.
5.
Do not allow pigs to
stand in a fully loaded truck, get moving immediately. Heat builds up rapidly
in a stationery vehicle.
6.
In winter, use straw for
bedding. In extremely cold weather, straw provides the best insulation and
helps prevent frostbite. Observations in packing plants indicate that trucks
with inadequate bedding are more likely to contain frost bitten pigs.
7.
When there is high heat
and humidity, it is best to transport pigs very early in the morning and at
night. Stocking density should be reduced.
8.
Schedule trucks so that
pigs can be unloaded promptly at the packing plant.
9.
Minimize the use of
electric prods. Electric prods should not be used in the finishing barn.
10.
Calm pigs are easier to
sort and separate then excited pigs. Pigs are easier to sort if the handler
moves slowly and deliberately and separates the desired pigs from the group on
the first attempt. Excited pigs stick together and are more difficult to
separate.
11.
If pigs refuse to leave
the finishing building, try shutting off the ventilation or reversing it. Pigs
often balk if air is blowing in their faces as they exit the building.
12.
To make pigs flow more
easily out the door of a finishing building, attach plywood to the last 16 feet
(5 m) of pen near the door. This will prevent pigs which are being driven out
of the building from seeing or touching pigs which are in pens near the door.
After loading, the plywood should be removed because it will interfere with
ventilation flow through the pens.
Packing
Plant
Practical
experience has shown that improving handling at the packing plant and reducing
electric prod usage will improve meat quality. Approximately 10% more pork will
be suitable for high quality exports to Japan when pigs are handled quietly and
usage of electric prods is reduced. Below are some tips for improving handling
in packing plants which will help maintain pork quality and reduce PSE.
1.
Rest pigs prior to
moving to the stunning chute for 2 to 4 hours. Slaughtering pigs immediately
after unloading will have a detrimental effect on pork quality.
2.
Use sprinklers during
hot weather.
3.
Staging areas which lead
to the stunning chute crowd pen should be filled only half full. Fill the crowd
pen only half full and DO NOT push the crowd gate tight up against the pigs.
They need room to turn.
4.
If pigs balk and refuse
to go up the single file chute or constantly back out of the chutes, look for
distractions that cause balking (Grandin 1996). Some of the things that cause
balking are: air blowing in the faces of approaching pigs, shiny reflections on
metal, puddles, a chain hanging in the chute, restrainer entrance too dark,
seeing people up ahead and moving objects. Removing distractions and improving
lighting will reduce balking. Light up the restrainer and chute entrances with
lamps. Animals will not go into a dark place. The lamps must not shine directly
into the faces of approaching pigs.
5.
Electric prods should be
eliminated in the yards and staging area. Pigs moved with electric prods had
higher heartrates than pigs moved with a panel (Brundige et al 1998). In the
stunning chute an electric prod may be needed on an occasional stubborn pig.
Some other tool should be in the person's hand as the primary tool for moving
the animals. The electric prod should only be picked up when it is needed. To
reduce use it should not be constantly in the person's hands. In a survey that
the author conducted for the USDA, (Grandin 1998) it was possible to greatly
reduce electric prod usage. In two plants which had excessive use of electric
prods 44% of the pigs were electrically prodded. After handlers were instructed
to fill the crowd pen only half full and tap the pigs first, the percentage of
pigs which were electrically prodded dropped to 15%. Handlers were able to keep
up with the line when electric prod usage was reduced. It is important to
eliminate distractions which cause balking. At another plant, it was impossible
to reduce electric prodding when the sun was out due to harsh shadows. When a
cloud covered the sun the pigs moved easily. To solve this problem, the roof
over the crowd pen had to be extended to block high contrasts of light and dark
at the stunning chute entrance. In plants where pigs are stunned in groups on
the flour electric prods should be totally eliminated.
6.
Monitoring of squealing
levels is a simple way to monitor stress levels during handling. When pigs are
quiet stress levels will be lower. Vocalization (squealing) is highly
correlated with physiological stress levels and poor pork quality. (Warriss et
al 1994, White et al 1995) In a slaughter plant an easy way to measure
squealing is to count the number of stun cycles where the entire handling area
is quiet. As each pig is stunned; score on a yes/no basis - "room
quiet" or "heard a squeal". From this you can calculate the
percentage of time the room is quiet.
Conclusions
Geneticists
and producers must work together to produce pigs which are easy to handle.
Genetically nervous pigs which have been raised in finishing pens where nobody
has walked the pens may be extremely difficult to handle at the plant. Quiet
handling at the slaughter plant will improve pork quality and reduce PSE. The
last 15 minutes in the stunning is the most critical time. Geneticists need to
select pigs which have a calm temperament and strong bone. One must be careful
not to over select for a single trait. There can be strange interactions of
traits. When the poultry industry solved their leg problems in large breasted
birds, a new weird trait emerged. Heavily muscled roosters with strong legs and
lower death losses are very aggressive and sometimes kill breeder hens.
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