November 22, 2008

Animal behaviour and welfare: Pigs Part 4


Behaviour problems: Overlaying piglets: Cures: Prevention

By Dr Clive Dalton

1. Overlaying piglets by the sow
  • This is a serious problem and accounts for 20% of all piglet deaths.
  • The greatest risk to piglets is during the first week of life and especially during the first few hours of birth when a restless sow gets up and lies down a lot.
  • The causes of high overlaying losses are complex and obviously involve the piglets and the sow. It's often difficult to apportion blame.
Factors in the sow:
  • Previous experience
  • Age
  • Breed and strain
  • Lameness
  • Leg and joint problems
  • Obesity
  • Skin parasites
  • Mastitis and udder problems
Factors in the piglet.
Piglets that are most likely to be crushed are usually one of the following:
  • Dull
  • Weak
  • Inactive
  • Uncoordinated
  • Suffer from coma
  • Chilled
  • Starved
  • Have very low birth weights
  • Have very high birth weights
  • Are runts from litters
  • Have splayed legs
Possible cures/Prevention
  • Provide a heat lamp in an area protected from the sow to attract the piglets away from her after suckling.
  • Place highly palatable feed pellets near the lamp to start the piglets eating.
  • This is most easily organised when the sow farrows in a crate, rather than free in a hut or pen. Sows usually lie with their teats towards the heat lamp.
  • Farrowing pens should all have rails about 200mm from the floor and 200mm from the wall.
  • Cull sows that persistently show this behaviour.
2. Savaging piglets by the sow
  • This is more common in inexperienced gilts with their first litter than in sows.
  • A sow may snap and injure an odd piglet, but seldom savages the whole litter.
  • The first piglet born is most likely to be savaged as it seems that the sow is frightened by it's movement and high-pitched squeak, associated with the birth process. Usually after the sow has sniffed the piglet, all is well.
  • Most sows accept human presence at birth, but strangers of unfamiliar noises may upset and frighten the sow and she may savage some piglets.
  • Sows that savage litters without very good reason are culled. Gilts may be given another chance but the fear is that the trait may be genetic and these animals should not be bred from.
Possible cures/Prevention
  • Check that the cause was not a "one-off" such as fright or panic and make sure it is not repeated.
  • Cull any female that shows the vice more than once.
  • Check the genetics of the female incase it could be an inherited trait.
3. Stress in pigs
Many factors have been identified as the causes of stress in pigs. These are all products of bad husbandry and/or poor stockpersonship:
  • Chilling
  • Overheating
  • Physical injury
  • Poor sanitation
  • Poor ventilation
  • Overcrowding
  • Bullying
  • Dampness and draughts
  • Genetic makeup
  • Weaning
  • Castration
  • Lack of feed and water
  • Nutritional deficiencies
  • Internal and external parasites
  • Disease
  • Loss of appetite
  • Noise
Possible cures/Prevention
  • Try to sort out which of the above is the main cause and change the management to avoid future problems.
  • Veterinary advice should be part of any changes.
4. Aggression - fighting in pigs

  • Aggression in pigs has been classified into three kinds - acute, chronic and abnormal.
  • "Acute" - fighting to establish a social order, especially when strange pigs are mixed.
  • "Chronic" - fighting to maintain an established order.
  • "Abnormal" - serious fighting that has very big economic implications.
  • Tail biting.
  • Ear biting.
  • Cannibalism.
  • Sudden savaging of a group member.
  • Sows attacking each other.
  • Sows savaging their young.
  • Domestic pigs unlike wild pigs are kept in monocaste social groups of the same sex, age and size. This may in fact make it harder and more stressful for pigs to form stable social groups when the combatants are physically equal.
  • Newly-acquainted pigs seem to fight for 24-48 hours to establish a linear dominance hierarchy, usually with the largest pig at the top and the smallest at the bottom. Note that it may not always be the biggest pig that becomes the top dominant animal. Once this is established, fighting is greatly reduced but not totally eliminated.
  • When unfamiliar pigs are mixed, fighting seems to start the feed runs out.
  • Fighting will nearly always occur when a pig removed for treatment is returned to the group. Top rank pigs can be returned without problems but any pigs lower in the social order will need to be returned before about a maximum of 3 days. The key to success is to know what the pig's social rank is before removing it and acting accordingly
Possible cures/Prevention
  • Check the environment to make sure it is not too hot or too cold, that the air is fresh and that the pigs have a dry warm area to rest.
  • Provide plenty of feeding and watering space. Hunger is often the cause of aggressive biting which can blow up into more serious aggression.
  • Make sure pigs are all of similar size in the group.
  • Provide bedding for newly mixed pigs to chew - at least for a period of about 1½ hours.
  • If pigs are removed from their group for any reason, try to put them back before 3 days. If they are the smaller members of the group, put them back sooner and watch that they are not victimised.

5. Tail biting and possible causes

  • This has developed since pigs were kept intensively.
  • Usually starts 4-22 days after weaning.
  • May be associated with ear biting.
  • There are many possible causes are put forward yet little is still known about it. The so-called "solution" is seen as removing the tail which should not be done before the causes are determined and rectified.
Causes are usually:
  • Behavioural - boredom, breakdown of dominance order or excess social contact.
  • Nutritional - low fibre, low bulk, and deficiencies of a whole range of nutrients.
  • Environmental - poor ventilation leading to high humidity, high temperatures, high ammonia and carbon dioxide, lack of bedding, and not enough feed or watering points.
  • Disease - skin mange, internal parasites and various infections.
  • Teething problems.
Possible cures/Prevention
  • Check ventilation to prevent build up of foul air.
  • Check pigs are not too cold (below 15C) and not too hot (above 28C).
  • Remove badly bitten pigs from the group and isolate them.
  • Daub the tails with Stockholm tar, creosote, disinfectant, lice of mange wash as a repellant.
  • Provide toys - hanging chains, paper sacks, straw, balls, stone filled cans, or anything you can think of to provide occupational therapy and keep the pigs busy.
  • Reduce the stocking rate in the pens - don't exceed 120kg live weight/m2 of floor space.
  • Group pigs on the basis of size. Often a small pig in a group is the aggressor and not the biggest one.
  • Move the problem pigs to another pen. This may fix the problem, or it can make them worse!
  • Change the feeding system or the physical form of the feed. For example moving from meal to pellets may help, or the reverse may work.
  • Keep mixing of pigs to a minimum as it may trigger fighting and make the problem worse.
  • Dock about 2cm from the piglet's tail at birth.
  • Change from flop-eared to prick-eared breeds as the incidence in the latter is sometimes less.

6. Cannibalism
  • This may develop from tail biting.
  • It often starts by pigs attacking wounds, prolapsed rectums, sick pigs and the like.
  • Pigs in a pen will chase and attack the suffering pig till it is killed - when they continue their cannibalism.
  • The attacked pig must be removed.
  • The remaining pigs must have a change to their environment - eg provide straw, altering the temperature, providing toys.
Possible cures/Prevention
  • See suggestions for tail biting.

7. Gastric ulcers
  • These increase as pigs are kept more intensively - clearly a stress induced problem.

Possible cures/Prevention
  • Try to find the cause and remove it - but may not be easy.
  • Investigate infections, intoxication, stress, gastric acidity, digestive upsets, hormones, seasonal changes, feeding methods (especially ad lib systems), housing and many more.

8. Nose rubbing (belly rubbing)
  • Weaned pigs may develop the habit of nuzzling other pigs as they lie resting.
  • It may appear is if they are navel sucking but it's more likely to be nuzzling in the flank area and along the teat line.
  • It may be accompanied by nursing grunts.
  • Persistent rubbing may cause ulcers and destruction of the tissue (necrosis).
Possible cures/Prevention
  • This is powerful thrusting by dominant pigs, after weaning, eg by high-rank males.
  • It occurs sporadically and can spread quickly through a group, and trigger off other vices like tail and ear biting.
  • The solution is to change environmental factors till you find something that does the trick.

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