Benchmarking Sow Lifetime Productivity

This measure more accurately describes the ultimate goal for producers.

By Ken Stalder, Linda Engblom, and John Mabry

The pork industry is becoming more interested in the length of time that sows remain productive within commercial operations. The interest in this trait is largely the result of the very tight economic situation that virtually all pork producers are currently experiencing throughout the world. Furthermore, the general public is becoming more concerned with the activities associated with the production of the meat they consume and animal well-being on the operations that produce this food. Furthermore, producers benefit when sows remain productive for a longer period of time in their breeding herds.

Because the costs can be spread across a greater number of piglets, producers are financially rewarded for having sows with an improved productive lifetime. The contrary is also true. If a particular producer is struggling with high replacement rate and he/she has a very high percentage of sows that do not remain in the herd long enough to pay for themselves, the producer is losing money. This type of situation slowly eats away at an operation’s equity until it is in financial trouble.

Typically, pork producers have used average parity at culling as an indicator of how their herd was doing from a sow longevity viewpoint. Of course, sow longevity is the length of time that a sow remains in the breeding herd. Examining the average parity at culling as a benchmark to see how we are doing as a commercial pork industry is informative. Table 1 shows the average removal parity from 1996 through 2004. These results are based on 515,194 sows removed from 132 farms during the period 1996 to 2007. To give the sows a possibility to show their real lifespan, only sows with their first farrowing between 1996 and 2004 were included. The average removal parity peaked at just over 5 parities in 1998 and has been on a slow, steady decline to just over 4 parities through the end of the reported data in 2004.

Not only should producers examine removal parity as a measure of sow longevity, but length of productive life or sow productive lifetime more accurately describes the ultimate goal for producers, so long as non-productive days do not increase above acceptable levels. Length of productive life more accurately describes the trait that pork producers are concerned with. This is the indication of how long individual sows remain productive (farrow a litter of pigs, lactate for ~ 21 days, return to estrus, successfully conceive, complete gestation, and finally farrow again).

How long sows remain productive can be measured in days of age from birth to culling, herd-life from entry into the herd through culling, number of successful parities completed, etc. The entire goal of this period is to produce as many pigs born alive and then as many standard pigs (i.e. full value pigs) at weaning as possible. This allows the initial cost of the replacement gilt and associated development expenses to be spread across a greater number of piglets produced during the sow’s lifetime.


There are numerous ways to measure the efficiency of the breeding herd. Many operations focus on litters per sow per year and pigs per sow per year. These values tell producers nothing about the lifetime productivity of an individual sow or on a herd-level basis. When all is said and done, the number of full-value lifetime pigs born alive, and lifetime number of full-value pigs weaned, combined with the price received for the pigs, determines whether the purchase of individual sows is a profitable decision.

Table 1: Average sow productive lifetime calculated on herd level (N=132) from U.S. pork producers participating in the Datashare program with PigCHAMP.


The different measures for productive lifetime can differ substantially within and across pork operations. Table 1 shows the variability for a number of sow productive lifetime traits. Because the actual age of the replacement gilt is often not known or recorded, the number of herd days is defined as the number of days from first farrowing to the removal event. The average herd life was 579 days and ranged from a low of 279 to a high of 982.

Assuming that gilts farrow at a year of age, you could add 365 days to these numbers to estimate the true age at culling. The average removal parity within this same data set was 4.5 and ranged between a low of 2.7 and a high of 7.1. When looking at how the top herds perform, the top 25% of herds average 641 days from first farrowing to removal and have an average parity at removal of 5. Similarly, the top 10% of herds average 727 days from first parity to removal and have a 5.5 average parity at removal. A closer examination of the average removal parity from Figure 1 shows that the most recent year (2004) where complete records were obtained, the average removal parity was just over 4 and is lower than the overall average. This suggests that on average, U.S. commercial pork operations are not doing as well from a herd-life standpoint as we were just a few years ago.


Producers incur costs when deciding to replace an old sow with a new replacement gilt. First, the replacement gilt has an initial cost; second, there are numerous development costs (vaccination, housing etc.); third there are breeding costs associated with getting the gilt mated and included in the breeding herd. Finally, not all gilts selected enter the breeding herd and hence, these sows incur all of the developmental and other costs that a gilt entering the breeding herd does. Those sows that do enter the breeding herd have to cover the expenses of the non-breeding gilts. These costs add to the initial cost of the breeding gilt. It is easy to see how a significant amount of money is invested in a replacement gilt by the time they enter the breeding herd. These costs are the same whether a gilt stays in the herd for only 2 parities or remains for 15 parities. At the end of the day, pork producers should think of their sows as investments; you should want to get as much of a return ($) as possible with each investment.

Figure 1: PigCHAMP Datashare herds average removal parity from 1996 through 2004

Since we expect sows to return as much income as possible in order for a pork operation to remain profitable over the long term, it is important to understand how producers can increase the returns for each sow. The number of pigs produced is the item that has value in a pork production operation. Therefore, the number of pigs born alive and subsequently the number of pigs weaned over the lifetime of the sow is what generates the economic value. As you might expect, the lifetime number of pigs born, pigs born alive, and pigs weaned vary substantially as shown in Table 1. It is important to examine both the number of lifetime number of piglets born and lifetime piglets born alive. The number of lifetime piglets born includes still born piglets or what is commonly referred to as fully formed piglets (excludes mummified piglets). The stillborn piglets may represent opportunity for number born live improvement if a producer can determine the cause and alter management practices to save more piglets at birth. Likewise, it is obvious that a piglet must be born alive before it can be weaned. Finally, examining the number of piglets weaned per lifetime is useful because the market has established a value for the piglet at that point. Furthermore, management can drastically impact the percentage of piglets weaned that are sold as full-value market hogs, which has little, if anything, to do with the sow that produced it. The herd average for lifetime piglets born, born alive and weaned were 51.8, 46.4, and 40.6, respectively. The range in the herd average for number of piglets weaned was from a low of 22.3 and a high of 64.1. The top 25% of herds averaged 45.2 lifetime pigs weaned while the top 10% of herds averaged 49.3 lifetime pigs weaned.


At the time of writing this article, the price for full-value weaned pigs on the spot market was approximately $36 per head. Using this number, combined with the average sow producing 40.6 pigs weaned, results in a gross revenue of $1,462. The range in gross revenue was from a low of $803 (22.3 pigs x $36 per pig) to a high of $2,308 (64.1 pigs x $36 per pig). Similarly, the top 25% of herd were averaged 45.2 resulting in a gross value of $1,627 (45.2 pigs x $36 per piglet) and the top 10% of herds averaged 49.3 lifetime piglets produced resulting in a gross revenue of $1,775. In a 2,500-sow operation, the difference between being an average producer with sows producing 40.6 pigs per lifetime and a top 10% producer who gets 49.3 pigs per lifetime means a difference of $782,500 gross revenue for the operation or over $300 per sow [$4,437,500-$3,655,000 = $782,500 (2,500 sows x $1,775 = $4,437,500 per sow gross revenue from a top 10% herd) - (2,500 sows x $1,462 = $3,655,000 per sow gross revenue from an average herd)]. This clearly demonstrates that the management to attain the greater productivity has significant economic benefit.

Examining the data from a sow level rather than from a herd level, the range in parity at culling is from 1 to 20 (data not shown) and the maximum lifetime number born alive and weaned were 224 and 173, respectively. As shown, occasionally you might even find the individual sow that can remain in the herd for 20 parities and produce as many pigs as 170 pigs weaned or even more in a productive lifetime.

We should not expect every sow or even the majority of sows to produce 20 litters and/or 170 pigs during their productive lifetime. However, these data demonstrate the management potential that exists within some herds and the genetic potential that exists within some sows to produce at such high levels.

Editor's Note: Dr. Ken Stalder, PhD, Dr. John Mabry PhD, and Dr. Linda Engblom, PhD are in the Department of Animal Science at Iowa State University, Ames, IA.