November 22, 2008

Animal behaviour and welfare: Pigs Part 3


Weaning: Stress: Growing pigs

By Dr Clive Dalton

  • In the wild, pigs are weaned at around 14-17 weeks old.
  • Farmed pigs were traditionally weaned at 8 weeks of age, but in more intensive systems weaning is done at 3, 4 or 5 weeks.
  • Even weaning at 24 hours after birth after the piglets have had their colostrum has been studied. But current opinion among pig behaviorists and welfarists is that piglets cannot effectively cope with weaning before 3 weeks old.
  • In some intensive systems, young pigs are kept very intensively in wire-floored tiered cages from weaning at 7 days. At about 7kg live weight, the pigs in these systems proceed to grow and fatten in "flat deck' cages on mesh floors.
  • The development of very early weaning systems is based on getting the sow pregnant to produce more pigs per year as weaning stimulates the sow to return to oestrus.
  • Abrupt weaning is now considered to be preferable to removing pigs gradually. Again this is to achieve higher production from the sow.
  • The more intensive the system is for growing pigs after weaning, the greater is the need for skilled care by the stockperson. There also needs to be a good smoke alarm system and back up for power breakdowns.
  • Studies of highly-intensive systems have shown wide variation from pigs showing stress behaviours, to pigs adapting well without stress. Clearly the person in charge who controls the pigs' environment is the key factor.
The stress of weaning

Weaning - whatever system is used, is a stressful time for piglets and stress is caused by:
  • Removal of their mother and hence their source of feed, warmth, security and comfort.
  • They lose their normal clues for feeding given by the sow's vocal messages.
  • They may be mixed with strange pigs from other litters and in a strange pen.
  • Competition for feed, water, sleeping space and dunging area may be increased.
  • They will face new bacterial challenges and diseases.
  • They may be subject to rough handling, transport, markets, veterinary inspection and treatment.
  • They will experience climatic change with cold temperatures and draughts being especially dangerous.
Reducing weaning stress
  • Piglets can cope with one or two of these stressors, but more that this leads to poor growth for up to 14 days after weaning.
  • The settling down period of pigs at weaning seems to be around 3 weeks.
  • The major aim is to ensure pigs are eating adequate amounts of correctly balanced dry feed before weaning. Flavour and physical form of this feed is important to encourage high intake.
  • Getting the pigs used to the lower temperature of the fattening accommodation is important. The sow's nest is around 28 C and they have to get used to temperature in the growing pens of 19C and eventually below this.
  • Avoid erratic temperatures, as this will cause pigs to huddle and fight for positions to keep warm.
  • Provide adequate trough space, again to stop intense competition and fighting.
  • Adequate lying space and a comfortable bed are important as growing pigs in intensive housing spend around 60-70% of their time resting/sleeping. Constant standing or restlessness will lead to fatigue and poor performance.

Behaviour of growing pigs
  • Poor growth and poor feed conversion inevitably will have a large behavioural component, especially in intensive systems.
  • There are many factors involved in poor performance, and the skill is to determine which of them can be changed, with the welfare of the animal as well as profit very much in mind.
  • The physical form of the diet is important. Pigs generally prefer wet to dry feeds, but dry feeds keep pigs occupied for longer.
  • Scattered feed takes longer to eat than feed in troughs - again keeping pigs occupied for longer. It also saves the costs of troughs and fighting over trough space.
  • Providing adequate trough space is of major importance, and prevents aggression and stress.
  • Feed offered ad lib will keep pigs fully occupied but restriction is often needed to control growth and performance. For example pregnant sows, as opposed to lactating sows, need their diets restricted to prevent them getting too fat. Obesity lowers subseqent lactation performance.
  • Pigs perform well on once-a-day feeding but feeding time is a good time to inspect pigs. Reduced appetite is a good early sign of potential health problems.
  • So it's important in large intensive systems to use time saved on chores to be spent on animal inspection.
  • This is especially the case as systems become even more automated where light levels are reduced. Increasing the lights for inspection will then activate the pigs, so there is a dilemma here.
  • Increasing stocking density/pen is an easy way to get more throughputs in a pig unit. It can have devastating effects on pig welfare.
  • This approach can cause a major upset in social order leading to bullying, tail and ear biting, disease, low feed conversion efficiency and low profits.
  • Pigs highly stocked in pens spend more time feeding, standing and walking, and less time resting and sleeping.
  • Contented pigs are recumbent for up to 19 hours a day. They drowse for 5 hours and sleep about 6-7 hours.
  • Pen floors have an important role in pig comfort and behaviour. They should provide a good non-slip, non-abrasive surface with no protruding edges, and not harbour bacteria or parasites. They should be impervious to water and be easily cleaned.
  • The pig's cloven hoof was designed to walk on earth, so slatted and perforated floors can cause damage and discomfort.
  • When social orders have been sorted out by fighting, all that is needed is a loud grunt and a feint with the snout by the dominant pig to maintain this order.
Mixing growing pigs
  • To reduce stress, mix pigs from 3-4 litters before weaning so they know eachother.
  • Don't put newly mixed pigs in too large a pen, as they'll stay in their original groups, they'll not mix and they'll fight to defend territory.
  • Put all the pigs to be mixed in a strange pen.
  • Distract them by giving them straw or paper sacks to chew, or spray them with a strong-smelling fluid.
  • Provide adequate trough space and feeding and drinking opportunities.
  • Mix them at dusk when identification of rivals will be more difficult.
  • Keep pigs in close weight ranges and remove any sick animals or any being severely molested.
  • The fewer pigs there are in a single group, the tighter they can be packed.
  • In general, vices are more common in large groups in large houses where social orders are more are more complex, and maintaining them causes more aggression and stress.
  • Don't change diets at the time when pigs are mixed.
  • Feed pigs ad lib diets for 2-3 weeks after mixing to avoid digestive upsets. Most producers feed ad lib for up to 10 weeks of age. Feed restriction should be delayed until the pigs have sorted out a new social order.
  • Provide plenty of feed and trough space.
  • Opinions on mixing sexes vary. Generally, if they have a good environment, sex does not cause problems. There may be some mounting in the last 4-5 weeks before slaughter.

Water for growing pigs
  • Water is provided from bowls, metal nipples or metal drinking straws. Pigs are very quick to learn how to operate them.
  • The watering device is a great plaything for bored pigs, so it will be subject to rubbing, nuzzling and chewing. Rigid construction is essential.
  • Place the water source near a dunging area or drain or above a food trough because of spillage.
  • Make the pigs have to reach up to get at nipples when drinking.
  • Don't put water sources in positions where pigs will bruise themselves. Put them in a corner.
  • Be consistent in the choice of drinkers provided.

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