Grandin Livestock Handling Systems
Colorado State University
Fort Collins, Colorado 80526
Producers have been giving pigs toys for many years to prevent boredom, reduce vices such as tail biting, and help prevent aggression when pigs are mixed. Providing pigs with additional stimulation will make them calmer and less excitable. Pigs raised in a barn with a radio playing are less likely to startle when they hear a sound such as a door slamming. Calmer pigs are more likely to have better meat quality because they will be less likely to become excited on a high speed slaughter line. A series of experiments were conducted at the University of Illinois by the author, Stan Curtis, and Ian Taylor to learn more about the effects of environmental stimulation on pig behavior.
Pigs have definite toy preferences. If a ball rolls into the manure they will no longer play with it. This is why we used toys suspended from the ceiling. Then the young pigs are given a choice between hanging chains, cloth strips, and rubber hoses, the animals prefer the cloth strips and the hose over the chain. In a short term initial preference test, the cloth strip was preferred. In a week long preference test the hose was the preferred toy.
Soft pliable objects were definitely preferred over the hard chain. There were two different behaviors the pigs performed with the toys. The behaviors were chewing or jerking and shaking. They shook the toy like a dog tugging on a towel. The pigs seldom jerked or shook the chain. It probably hurt their mouths. Pigs will play with chains, but they prefer to play with pliable objects when they are given a choice. The pigs performed a wider variety of behaviors with the pliable objects.
The purpose of the next series of experiments was to determine the effect of different environmental enrichments on behavior and handling of confinement reared, finishing pigs. All pigs were reared in a closed, environmentally controlled house. Landrace sired crossbred pigs were subjected to four different treatments during the last five weeks of finishing. The treatments were:
People never entered the pens, but the pigs could see people in the aisle and in adjacent pens.
a person entered the pens and gently petted the pigs for five to ten minutes once a week for five weeks.
Some pens of pigs were subjected to combinations of the treatments.
In Trial 3, two different types of mingle treatment were used, an Assertive Mingle and a Gentle Mingle. In Assertive Mingle, the person petted every pig, even if it attempted to avoid the person. In Gentle Mingle, only pigs which approached were petted. The Gentle Mingle method was used in Trials 1 and 2.
All environmental enrichment treatments definitely reduced excitability. Animals that had a combination of two or more treatments were rated less excitable then animals with a single treatment. Excitability was measured on a 1 to 4 rating scale. Two raters entered each pig pen at the end of the trial. The rating was blind. The raters did not know which treatments the pigs had been on. The higher the rating the more excitable the pigs. Pigs with a rating of 4 actively avoided the rater and piled up and squealed. Pigs with a rating of 1 were calm and often approached the rater.
Effect on Weight Gains
Some producers may be concerned that these treatments would stress the pigs and lower weight gains. This did not occur. None of the treatments had an effect on weight gains. It is of the utmost importance that the mingle and driving treatments are done gently. Our pigs appeared to "enjoy" the weekly walks in the aisle. They ran excitedly down the aisle. If animals feel threatened or intimidated weight gains will suffer. Australian scientist Paul Hemsworth found that inconsistent handling stressed pigs and reduced weight gains. If the handler occasionally slapped or shocked the pigs when he entered the pens, the animals became stressed each time he approached. Even if the handler is gentle and nice most of the time, the pigs learned that he is not to be trusted. How an animal perceives a situation during handling can have a big effect on stress levels. Procedures such as weekly weighing will usually have little effect on weight gain if the animals have learned that nothing bad is going to happen. Weekly weighing may have a detrimental effect on weight if the pigs see the "mean" man who shocked them with a prod. Most animals are smart enough to associate certain people with painful experiences. It is doubtful that baby piglets associate a particular person with castration. These animals are so young that the brain is probably too immature to store specific memory.
Stimuli which may initially frighten a pig can often become pleasurable. During pen washing the animals squealed and became excited the first few times. By the third or forth washing the animals appeared to eagerly anticipate pen washing. They approached and played in the water. Some turned broadside to get the full blast of the water.
Effect of Experience and Genetics
Some breeds or genetic lines within a breed will remain calmer in a barren environment than others. Both genetics and experience prior to finishing will effect how a specific finishing pig will react to enrichment. Hemsworth has also found that baby pigl ets which receive frequent gentle handling are still tamer weeks later. They are more likely to approach strange people.
The effect of toy, mingle and driving treatment on handling was tested on Landrace sired crossbred pigs. In the first trial, mingle and toy treatments reduced the force required to drive pigs through a chute. In the second trial, the controls were slightly easier to drive. The mingled pigs had become so tame that driving was difficult. The pigs used in the second trial were tame and calm before Trial 2 started. The pigs used in Trial 1 were more excitable than Trial 2 pigs at the beginning of the experiment. The animals in Trial 2 also received more frequent pen washing. This provided additional environmental enrichment that commercial pigs do not receive.
There may be an optimal level of stimulation for animals that will be marketed for slaughter. You want a calm animal which will not panic and become excited, but on the other hand, you do not want an animal that is so tame that driving is difficult. This principle does not apply to breeding stock. Breeding stock benefit from lots of tender loving care. Tame sows and boars are easier to handle and have better productivity.
The amount of contact with people that will produce a calm, easy to drive market pig is going to vary. Genetic factors will interact with previous experiences. Pigs which are very excitable would require more contact with people in the pens than calm pigs. Most confinement reared finishing pigs would probably benefit from toys and a radio. Pigs differentiate between people in the aisle and people in the pen. For maximum effect the person must enter the pen.
Environmental enrichment procedures improve welfare. Many experiments have been conducted on the effect of sensory restriction on animal behavior and physiology. Dogs, rats, and other animals reared in a barren environment will become hyper-excitable. They will react strongly to small stimuli which would hardly be noticed by animals reared in a more enriched environment. Pigs raised in confinement buildings with little contact with people sometimes react in the same manner as the animals described in the sensory deprivation literature. I want to emphasize that only some confinement reared pigs have this problem, not all of them.
About thirty years ago, a number of sensory restriction, experiments were performed on young dogs by R. Melzack. The animals were placed in barren kennels. They could hear and smell other dogs. This was not total deprivation but a barren, restricted environment. The dogs became hyper-excitable, and they had abnormal brain waves. The brain waves were still abnormal six months after the dogs were returned to a household environment. Genetic factors also play a role. Some breeds or genetic lines within a br eed will become more excitable when subjected to sensory restriction than others. Simple environmental enrichment procedures will prevent pigs from showing the symptoms of sensory restriction. Playing a radio, with a variety of music and talk, in the barn will greatly reduce frenzied jumping about when a person enters the room.
Environmental enrichment procedures have the potential of improving meat quality. Hot, excited pigs are more likely to have poor quality meat. Canadian research indicated that overheated pigs have a much higher incidence of DFD or PSE meat. Danish research and observations made by the author also indicate that gentle handling at the packing plant improves meat quality.
Observations at large slaughter plants indicate that some groups of confinement reared pigs are highly excitable and difficult to drive. Other groups of confinement reared pigs are easy to drive. Animals that are difficult to drive are more likely to be zapped with electric prods to keep them moving onto a high speed slaughter line.
Previous studies in Europe indicated that rearing environment had little effect on meat quality. The failure to find differences is probably due to very gentle treatment at slaughter. In one experiment the pigs were slaughtered in groups of eight. If the pigs had been subjected to the stresses of a high speed line, there is a good possibility there may have been a difference. Paul Warris in England reported that confinement reared pigs were more excitable than the pigs reared outside, but the effect on m eat quality was minimal. Excitability will probably have little effect on meat quality if the pigs are slaughtered under optimal conditions, in a quiet meat laboratory or a small abattoir. Pigs slaughtered in commercial plans at 1000 per hour are subjecte d to rougher handling. Pigs which balk and refuse to move will receive more electric prodding.
There may also be an interaction between genetics and environment. Reducing excitability may have a greater effect on meat quality in some types of pigs compared to others. A. Fortin from Canada recently reported that the beneficial effects of rest prior to slaughter varies. Stress resistant pigs benefited more than the stress susceptible pigs. Overall, resting pigs for a few hours prior to slaughter will improve meat quality. The amount of improvement is going to vary greatly between different groups of pigs.
There are other physical problems which make some pigs almost impossible to handle at the packing plant. Some Landrace pigs have weak rear ends and they often fall down and split. This problem can be corrected by a change in breeding program. Overcrowding of finishing pens also contributes to handling problems. Pigs finished on metal mesh floors are extremely difficult to drive at the packing plant. These animals grow excessively long hooves and they do not know how to walk on concrete. They balk and balk and balk. Pigs raised on concrete finishing floors are easier to handle. Most producers do not use metal mesh floors for finishing, unfortunately there are a few equipment companies that still install metal mesh in finishing barns. Recently I designed a handling facility for a large packer. I had to design a special unloading chute which bypassed the scale and tattoo area for the "metal mesh pigs". Recently I discovered that a construction company is still building barns with this terrible flooring. The construction companies use metal mesh flooring because it is cheap. The company has told producers that finishing pigs on metal mesh flooring provides better gains and conversion. This type of floor is good for younger pigs but it will not improve the performance of finishing pigs.
The development of simple economical environmental enrichment procedures can improve animal welfare and possibly improve meat quality by calming down excitable pigs.
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