Building on the impact of weaning age on other, select performance parameters discussed last week, let’s take a look at weaning age effects on wean-to-first service interval, farrowing rate, farrow-to-farrow interval and female death loss.

Since we get data from over 20 different sow recordkeeping programs, there is some question about how various programs handle and record nurse sows, partial weans and crossfostering. Each farm needs to review how their sow record program calculates weaning age of pigs at their farm.

The information in Table 1 shows data from 686 farms with 1,211,000 females that are producing at 20+ pigs weaned/mated female/year (PW/MF/Y). The accompanying data (Charts 1-15) are sorted by weaning ages: less than 18 days of age (70 farms), 18 days of age (126 farms), 19 days of age (172 farms), 20 days of age (163 farms), 21 days of age (72 farms), 22-23 days of age (57 farms) and 24+ days of age (26 farms). We have summarized four areas that are then broken down as follows: Average Top 10%, Top 25%, Top 50%, All, Bottom 50% and Bottom 50% based on PW/MF/Y.

Chart 1 shows wean-to-first service interval decreasing as weaning age increases, but it is not a linear progression. The average of all farms ranged from 7.48 days for the farms weaning under 18 days of age to 6.60 for farms weaning over 24 days of age – a 12% improvement.

The Top 10% of farms improved from 6.86 to 4.74 days – a 31% improvement. The biggest improvement in this group is from 22-23 days of age to 24+ days of age, however, this is misleading because there are only three small farms in the Top 10% at 24+ days.

The Top 25% of farms improved from 7.08 to 5.61 days for a 21% improvement. Even the Bottom 25% of the farms improved from 8.40 to 7.47 days – an 11% improvement, the smallest improvement by any group.

Charts 2 through 5 show the trends by weaning age group for the last 12 quarters. Some of the improvement is from weaning older pigs, however, most of the improvement is in how the sows are being fed during lactation. Monitoring feed intake is key to improving wean-to-first service interval. The target should be 14 lb./day or more.

Chart 6 is farrowing rate broken down by weaning age. Farrowing rate generally decreased as weaning age increased from less than 18 days to 19 days, then showed small increases as the weaning age increased from 20 to 24+ days. The largest increase was for the Top 50% farms at 2.3% improvement and the smallest increase was for the Top 25% group at 0.8% improvement.

Charts 7 through 10 show the trends by weaning age group for the last 12 quarters. In looking at the trend charts, there are other variables affecting farrowing rate besides increasing weaning age. There is still some seasonal effect to farrowing rate. Farrowing rate is more affected by the quality of the boar semen, skill of the artificial insemination technician and proper timing of the insemination.

Chart 11 show farrow-to-farrow interval, which increased for all groups. The spread for the less than 18-day weaning age is 14 days (145 days to 131 days), but when looking at the 24+ age at weaning, the spread is only two days (from 148 to 150 days).

Charts 12 through 15 show the trends by weaning age for the last 12 quarters. Note the 5-6 day increase in the farrow-to-farrow interval as the weaning age goes from less than 18 days of age to 24+ days of age.

The increase in weaning age has lowered the wean-to-first service interval, but has also increased the farrow-to-farrow interval. It also appears the fertility of the sows is not significantly affected by the weaning age increase. This tells us there are many variables affecting farrowing rate besides weaning age.

Key Performance Indicators
Tables 2 and 3 (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