Recently I’ve read an assortment of opinions about the best parity distributions for sow herds. Many of them appear to derive from the parity profiles of top-producing herds. When asked what his ideal parity structure would be, my Ph.D. advisor, Dr. John Deen, used to say that the ideal parity distribution would be horizontal through parity six and then drop off steeply. That’s because, ideally, there would be little death loss or culling and all sows would survive through their most productive middle parities. Today I’ll add my own two cents.
When we think about parity structure, there are two important considerations. First, sow durability varies tremendously across genetic lines. And second, the herd’s parity structure is really a function of the sow survival curve—that is, how many sows successfully make it into the subsequent parity.
A number of models have been developed to consider optimal cull parity. Some models assume that sows should be culled when their productivity costs are equivalent to their investment costs. Others suggest that a sow should be replaced only when a replacement will generate more revenue for the herd than retaining that sow. Other field-based recommendations stem from observations in highly productive herds. If only we could duplicate the parity structure of highly productive herds, then we, too, could observe high productivity—never mind any differences in system constraints.
That being said, the best way to determine a herd’s optimal parity structure may be to look within and ask, which are the most productive parities? If the first parity is most productive, then parity structure becomes a function of balancing out the costs of the incoming females with the anticipated latter-litter performance of sows in the herd, i.e., sows would be culled when their production revenue and replacement costs reach breakeven.
Alternatively, if the herd’s most productive parities are the middle parities (i.e., parities 3-5), then the herd’s optimal parity structure should reflect an effort to maximize the proportion of sows reaching those parities. Not only does this make good production sense, it also makes good economic sense. Newly established herds, no matter how rocky the start-up, often see a boost in production during their second and third years. This is because, short of a rapid-rollover or expansion project, the herd parity structure will never again be able to achieve as great a proportion of its animals in those most productive middle parities.
Pig production is not a universal franchise with universal recipes and uniform output. In fact, there are few universal recommendations in pig production, and a universal recommendation for herd parity structure is certainly not among them. Each herd and system has to balance its productivity concerns with its logistical and economic constraints. And as with many of the questions producers face, the answers lie in the production records.
Editor’s Note: Dr. Stephanie Rutten-Ramos is an independent consultant. To visit with her, send her an e-mail at: rutt0011@umn.edu
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