That is the question facing every sow unit. Some culling decisions are straightforward. Animals that have health problems or lameness issues need to be removed from a herd out of concerns for their welfare. But, what about those less-than-stellar performers -- who should stay and who should go?
In reality, many culling decisions are driven by replacement gilt flow. If gilts are in the pipeline, sows can be removed. If not, the herd could retain the otherwise cull candidates and accept the risk of decreasing sow productivity averages. Those sows could be removed, but the herd then runs the risk of decreasing the unit's total output.
As with all pig production, nothing is as simple as it seems. Sow removal programs may impact sow-unit productivity, but their replacements also impact the level of productivity in the nursery and finishing phases.
In the latest issue of the Journal of Swine Health and Production, a team of Iowa State University researchers reported that Parity 1 offspring were significantly lighter than offspring of other parities at 42 days post-weaning. Their results are consistent with other studies that have reported similar effects of first parity females on pig survivability and weight at the end of the respective production phase. These findings reinforce the benefits of segregating Parity 1 offspring at weaning to allow those pigs a longer grow-finish phase.
One of this industry's great challenges is finding that balance between the sow unit's interests and the interests of nurseries and finishers. As we watch annual sow replacement rates continue to climb, it is important to not lose sight of the implications down stream.
There are neither easy nor universal answers about how best to make culling decisions. Each program needs to be herd-specific/system-specific. And for systems looking to optimize overall productivity, the effect of the replacement female's offspring needs to be taken into account.
Stephanie Rutten-Ramos, DVM
University of Minnesota
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