The Swine Management Services (SMS) database is seeing an artificial improvement in pigs weaned/mated female/year (PW/MF/Y). As we updated the “all farms” database at the close of the third quarter, we saw a 5-10% reduction in the number of females per farm and fewer total sows. About 30 farms closed. However, with new farms added to the SMS benchmarking database, the total number of farms increased.

When 10% of the sows are farrowed, weaned and then culled, a 5-10% increase in the standardized PW/MF/Y may result. There are many ways to calculate PW/MF/Y, so it is very important to review how your recordkeeping program calculates this number.

An example of how a change in sow inventory affects PW/MF/Y: A 2,500-sow farm is weaning 120 sows (1,200 pigs/week) with a PW/MF/Y of 25.03. As the farm reduces the sow inventory by 10% over a 16-week period, the farm continues to produce 1,200 pigs/week. After 16 weeks, the sow inventory will drop to 2,250 sows, but the “average” sow inventory over that 16-week period is 2,357 sows. This would calculate to 26.54 PW/MF/Y, which is a 6% improvement with no more pigs out the door. It will take a year after the sow inventory reduction starts for this number to come back to 25.03 PW/MF/Y, assuming reproductive performance holds steady.

Chart 1 (attached) shows the PW/MF/Y trend lines for the Top 10%, Top 25%, Top 50% and All Farms beginning in July 2006, updated monthly. Over that period, the “all farms” PW/MF/Y average increased from 22 to 23.4 pigs.

Farms that are reducing their sow inventory, then increasing the weaning age of the pigs, should see total pigs born increase over the next 12-18 months. It is possible for a farm to decrease sow inventory by 10% and within 18 months be producing the same number of pigs per week as they were at the time the inventory reduction began.

A rule of thumb to remember is – as weaning age increases by one day, the subsequent litter will increase by 0.10 pigs, total born. Therefore, as you decrease sow inventory, you are able to wean pigs three days older and your “total born/litter” may increase by 0.3 pigs. At 2.4 litters/mated female/year, the PW/MF/Y increases by 0.72 pigs.

Key Performance Indicators
Tables 1 and 2 (below) provide 52-week and 13-week rolling averages for key performance indicators (KPI) of breeding herd performance. These tables reflect the most current quarterly data available and are presented with each column. The KPI’s can be used as general guidelines to measure the productivity of your herd compared to the top 10% and top 25% of farms, the average performance for all farms, and the bottom 25% of farms in the SMS database.

If you have questions or comments about these columns, or if you have a specific performance measurement that you would like to see benchmarked in our database, please address them to: or

Click to view graphs.

Mark Rix and Ron Ketchem
Swine Management Services, LLC