Zeroing in on Female Retention Rates

Several groups and individuals have asked if we look at female retention rates. We haven’t been doing so since there is a large variation from farm to farm when data on gilts are entered.

March 11, 2013

6 Min Read
Zeroing in on Female Retention Rates

Several groups and individuals have asked if we look at female retention rates. We haven’t been doing so since there is a large variation from farm to farm when data on gilts are entered.  Since more sows record programs have gone to billing the farm for the female inventory vs. a yearly fee for the farm, more farms have stopped entering the purchase date of gilts. A lot of farms enter the data for the gilts when they move them to the breeding area.

Gilt development has been an area of interest for us for several years as it serves as a key to female retention and improved production numbers. 

When we conduct a further analysis of farms in our database, it shows there is a lot of variation in female death loss. Based on parity, we find farms with 30-45% of the female deaths being P0 and P1 females. Whether purchasing or raising your own replacement gilts, high death loss increases the cost of gilt development.  In turn, that increases the cost to produce a weaned pig.

To investigate further the subject of female retention, we reviewed data from 87 farms that had been in production at least three years.  

Table 1 summarizes the data from these 87 farms. These farms have an ending inventory of 197,409 females, which is an average of 2,270 females per farm. Over the last 52 weeks, producers have entered 101,414 gilts into the farms. The annual replacement rate was at 51.4%; the database is broken down by parity from P0 to P7+.  The average cull rate was at 44.8% and death loss was at 7.2%.

In Table 1, the culls and deaths are broken out by parity with an average of 11.6% of the culls and 11.5% of the female deaths being P0 females. That means that 23.1% of all the gilts that entered the system did not farrow a litter.  When you look at the P7+ females, this group represented 12.5% of the culls and 9.3% of the female deaths, or 21.8% of the total animals removed.


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Table 2 depicts gilts on farms broken out by Entry to 1st Service Interval (days). The range was from 0 to 150+ days. The 0 day farms means gilts were entered and bred the same day. The 150+ day farms could be entered as a weaned pig or feeder pig.  Some farms bring in gilts on a weekly or monthly basis and others purchase multiple age groups of gilts every 8+ weeks.  By doing so, farms can reduce hauling costs for purchasing gilts, limit the number of entries to reduce biosecurity risks and reduce gilt acclimation time before transport to the sow farm.  This helps to lower health challenges to the incoming gilts and the sow farm.

Farm that basically enter gilts when they are bred underestimate their true female death loss and replacement rate (Table 2).  It’s unknown what happened to a very high percentage of the purchased gilts and whether the database reflects the cost to raise a replacement gilt or not. 

To look at the extremes for the day’s Entry to 1st Service Interval, we created Tables 3 and 4. Table 3 is the five farms with Entry to 1st Service of 150+ days.  The average size of these farms is 3,691 females.  The overall replacement rate was at 68.9% with female death loss at 6.7%. Some 22.5% of the total culls and 19.2% of the total female deaths were P0 females, representing 2,794 gilts, which was 21.9% of the 12,713 gilts that entered the farms.

In Table 4, there are nine farms that have an Entry to 1st Service Interval that is <1 day, for which you see a drop in replacement rates to 50.8%, and female death loss is at 7.7%.  There were 10,209 females entered, with only 743 being culled and 132 female deaths, for a remove rate of only 8.6%. That compares to farms at 150+ days for Entry to 1st Service Interval, with a removal rate of 21.9%. The reason for the big variation is only gilts that made it through development were entered, and the other gilts purchased that were culled or died are not part of the records. The farms with 150+days account for all females culled and that died.

The last line in Tables 3 vs. 4 depicts the percentage of females retained to next parity, which is a large variation with  P0 at 86% vs. 96%; P1 at 75% vs. 89%;  P3 at 65% vs. 79%; P5 at 57% vs. 71%; and P6 at 53% vs. 68%.

Large variation in replacement rate and Entry to 1st Service Interval for the 87 farms is illustrated in Charts 1 and 2.  For the last 52 weeks, replacement rates ranged from a low of 22% to a high of 78% and Entry to 1st Service Interval ranged from 0 to 230 days. 


In summary, not knowing the age of the gilts purchased or selected makes it difficult to determine the Entry to 1st Service Interval. This lack of information makes it hard to perform an accurate comparison between farms on culling rate, death loss rate and determine the true retention rates.  The difference between a 50% replacement rate and a 60% gilt replacement rate could be due to how gilts are entered into the records program and not how fast the farm is turning the breeding herd.

Past “Production Preview” columns can be found at  Click on “newsletters,” then the respective date of the Weekly Preview issue you are interested in.

Key Performance Indicators

Tables 5 and 6 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 KPIs 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:  [email protected]or [email protected].


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