Try to mix pigs as little as possible. Varley (2001) showed that litters kept together grew 110g/day faster to 20 days post-weaning.
My own work (2003) into justifying 'big pens' showed that pigs split into 4 pens rather than into one big one grew 13.5% slower from 10 – 92 kg., their feed intake fell by 7.2% and food conversion worsened by 7.2%. Stocking density, feed and water allowances were all up to par. But we all have to mix pigs at one time or another…….
*The big error is to fail to allow sufficient space for submissives to avoid dominants and for dominants to get their challenges over with minimal damage to either party.
* Try to allow 20% more ground plan to that from which they came. Young pigs will grow into it and everyone tends to overstock these days.
*Feeder space and drinking space. The majority of aggressive incidents occur close to the feeder and this is why an extra feeder or hopper for a while after mixing is advisable.
*We have all learned now that two drinkers are advisable in every pen including those with wet/dry feed hoppers as these are only food-moistening/better feed-intake devices, not adequate water sources. And one drinker is essential even in pipeline-fed layouts.
*If possible reduce the feed allowance by a quarter from the morning of mixing day.
*Introduce the pigs just before dusk, certainly not by mid-afternoon.
*Allow ample food once the pigs are moved.
*Spray the pigs with lavatory freshener aerosol once they are mixed.
* If using bedding, re-bed amply just before mixing.
*Place some of the to-be-mixed pig's faeces in the voiding area.
*Do not batch too evenly, especially young pigs out of the nursery. A 4 kg range in an 30-35 weight band is better than identical weights (Lean, 1985) and at 21 to 28 day weaning, a 1 to 1.5kg range difference may be best for groups of 20 to be grouped together. This allows dominance to be established quicker.
*In larger 'big pen' groups now gaining favour, once the group size reaches 50 to 100 animals the reduction in weight gain after weaning begins to disappear – one of the several reasons for its popularity.
* Watch stocking density in relation to pen shape. Pigs in long, narrow pens need more space to allow the submissives to escape. Fairly squarish oblongs are best.
* That first night's rest together is important, when 'stranger scents' get rubbed-off and mingled by dawn. Allow ample resting space and in winter a temporary cover placed over the sleeping area makes for cosiness in a strange place, discouraging nervous 'sleeping out' by the submissives which can cause tail biting later on.
If any of you have any tips on mixing which you find work - please share them.
Mixing sows is another skill which I will deal with next time.