One of the successes in pig production has been an almost continuous increase in sow herd productivity. Sow herds have continued to increase the number of pigs produced per inventoried female per week.

Figure 1 on page 8 shows the trends seen in the industry, as portrayed through the PigChamp benchmarking program, depicting pigs weaned/mated female/year.

There have been improvements in the productivity of the North American swine herd, but the past few years have seen some flattening out of those improvements.

Nonetheless, the improvements have ensured that adequate pigs are available within most systems, at least on average.

Quantity to Quality Shift

The concerns about the sow herd have turned from a simple measure of the total pigs produced, to measuring the quality of the individual pigs and the flow of pigs out of a sow reproductive unit.

As we look at reproduction as a discipline to ensure a quality product, and an efficient utilization of the overall pork chain, we can identify several opportunities for improvement.

The sow unit must be a supporting enterprise for the entire pork chain system. Unfortunately, in many cases, we have not adequately focused on the need for high-quality productivity from the sow unit. Grow-out facilities are often a captive client of the sow unit, and inadequate communication and sharing of records occur in many situations.

Weaning Age Debate

As we look more closely at the need for coordination, various sow output parameters are being revisited. The most publicized choice in this discussion is weaning age.

Though it can be argued that increasing the weaning age decreases the productivity of the sow herd in some cases, in most cases that increased cost to the sow herd is recouped through increased performance of progeny downstream.

Figure 1 shows such a relationship, illustrating that the likelihood of success in the nursery is directly related to the weight and age of pigs at weaning. This balancing of costs and benefits can only be made when projects are correctly evaluated. Costs are not a problem, but benefits need to be captured downstream.

Seasonal Variation

It is not only the quality of pigs that should be evaluated, but the problems in seasonal variation. Figure 2 helps identify seasonal variation in output as a major problem in the American swine herd.

The amount of seasonality in weaned pig production leads to inefficient use of facilities, both in growing out pigs and at slaughter. Even worse, the seasonal supply is put against a retail pork demand that is relatively static. That's why we see seasonal price variation that can be as high as 25%.

There is a very strong case to be made that the major disease problem in the American swine herd is actually seasonal infertility. No other condition leads to such a variation in supply, nor to such an effect upon prices.

As we have looked more closely at the problem of seasonal infertility, we have found that two broad mechanisms should be considered.

First, the worst seasonal infertility occurs in herds that have marginal fertility during the winter. In other words, if proper methodologies and management are not utilized during the winter breeding period, the sow herd is exposed to a higher risk of fertility problems during the summer.

This scenario suggests that control of seasonal infertility is within our reach using methodologies already available. It should also be emphasized that the first and major mechanism of seasonal infertility is reflected through reduced farrowing rates and smaller litter sizes (Figure 3, page 10).

The second broad mechanism of seasonal infertility is the response to this so-called “disease.”

As seasonal infertility progresses through the summer, sow herd size will increase. As pregnancy rates drop, more sows are retained and the proportion of open sows increases.

Complicating matters further, seasonal infertility appears to end quite quickly, the proportion of sows successfully bred increases, and, subsequently, the result is overproduction of the sow herd.

This cyclical under- and over-production of the sow herd leads to variation in weaning weight and variation in grow-out performance.

As previously suggested, Figure 1 shows the relationship between weaning weight and the likelihood that a pig will be produced at an adequate weight.

Pig weight has often been measured as an average, but it is the distribution of weights, and the existence of low-weight pigs in particular, that leads to problems in the nursery. Much of the mortality problems and issues of slow growth are concentrated in these pigs.

Though weaning weight is a major predictor of subsequent performance, factors such as the manipulation of litter size and its impact on weaning weight have not been taken into account.

With lower weights, the likelihood that a weaned piglet carries a pathogen is a major concern. Factors such as parity, weaning weight, season, and of course, disease status of the sow herd, are all major concerns.

In addition, the proportion of gilts in a farrowing group has been found to be a predictor of disease outbreaks. Minimizing culling rates has often been argued on the basis of sow herd performance.

Perhaps an even greater emphasis should be placed on the quality of the progeny. Many cases have shown where stopping the introduction of gilts sometime before a planned depopulation has reduced the amount of disease in the nursery.

Moreover, culling is detrimental unless it is focused on older sows. Culling rates should be minimized, but the focus should be on reducing the culling of sows with less than three parities. This approach improves reproductive and progeny performance.

In some ways, the savvy production unit can be considered an input supplier to the pork chain that can be treated similar to a feedmill. It must provide a high-quality product, and it must have adequate capacity to meet the requirements of downstage production.

Unfortunately, the value of a unit's output is such that even if it overproduces, that product is put into the pork chain.

Stable production of robust progeny that do not transfer pathogens is our aim. It should also be our focus in measurement and optimization.