Tonisity Tips – Sorting by Size and Sick Pens at Weaning
At weaning, the variation in weight among a cohort of pigs that only differ 1-2 days in age is around 22-25% when measured by the coefficient of variation. Because of the large variation at weaning, many producers assign weaned pigs to nursery pens based on their relative size. The ‘large’ pigs are placed in pens with other ‘large’ pigs, the ‘medium’ with ‘medium’ and ‘small’ with ‘small’. While this makes for pens of uniform-sized pigs at weaning, it does not result in a similar uniformity at the end of the nursery period. Research trials have repeatedly demonstrated that pens of uniformly-sized pigs at weaning have increased variation at the end of the nursery period, while pens with large variation at weaning have reduced variation at the end of the nursery period. Another common mistake pig barn personnel often make is to leave several pens in a facility un-stocked at weaning. The remaining pens are over-stocked to accommodate the facility stocking density.
The goal is to remove ‘small’ or apparent disadvantaged pigs to these un-stocked pens in the first few weeks after weaning. Often times these removals aren’t routinely done, meaning the existing pens remain overstocked, while the un-stocked pens become ‘dust-collector’ pens. Even when the pens get stocked with pigs removed from other pens, the pigs may not respond as desired.
If the pen into which the pigs are placed after removal from another pen doesn’t result in the pig receiving special treatment such as a heat lamp, a special diet, a special feeder, a draft barrier, etc. the pig that is relocated in fact becomes disadvantaged since it now must compete for resources with other relocated pigs leading to social stress. The general rule should be that a pig is not relocated to a pen (often identified as a sick pen) unless something special is done with pigs in the sick pen that improves their chances of recovery and growth.
Another management failure often observed on farms is allowing pigs removed to sick pens to continue to deteriorate in body condition. When a pig is removed to a sick pen, the goal should be either a marked improvement in its condition in 5-7 days followed by relocation to a ‘graduate’ pen or the decision is made to euthanise the pig in a humane manner to relieve its’ suffering. While euthanasia is difficult for many pig farm employees to carry out because of their concern for all pigs, recognition of the need to relieve a pig of its suffering is something that needs to be stressed with all barn workers.
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