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Save Money by Keeping Sows Longer
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You may be further ahead by giving sows a second chance as opposed to culling them right away.
By Linda Engblom, Ken Stalder and John Mabry

Sow removal is receiving more attention due to its impact on economic and animal well being considerations. High removal rate of
breeding herd females is associated with poor longevity. When the average longevity is low, improvements can be highly profitable
(Sehested, 1996). A decreased removal rate of sows reduces the costs for replacement gilts and thereby increases net income.
Studies have shown that it takes at least three litters before a sow provides a positive cash flow for the producer (Lucia et al., 2000;
Stalder et al., 2003). Reducing high replacement costs due to high removal is especially important today when the pig production industry is operating on very slim profit margins. The input cost for a gilt is the same, no matter how many parities she produces. Gilts should therefore
be considered an investment that should be used as effectively as possible.

Breeding stock suppliers recommend removal of old sows to allow genetic progress to be implemented on the farm. However, that is not the problem in the present environment. In 2007, the average culling rate in the United States was 49%, and average death rate was 9% (2007 summary of PigCHAMP database). This means that more than 50% of the sows, on average, were replaced. Removal of sows from 132
farms during a period from 1996 to 2007 was evaluated. Sows farrowing for the first time from 1996 and 2004 were included, resulting in 515,194 removed sows. Results presented in Table 1 are averages from these 132 herds.
     The average parity at removal was 4.5. Figure 1 shows that 18% of the sows are removed after parity 1 and that only 15% are productive through eight litters. So today, the problem is not too many old sows on the farms but too few sows that reach the higher parities. Typically, litter size increases up to parity five, but today fewer than 50% of the sows produce five litters.


Sow removal includes both culling and mortality. Removal of old sows is a natural
component of piglet production and is called “planned removal.” Planned removal also
includes removal of sows with low productivity. Planned removals are not the challenging
part of pork production, but unfortunately, only 20% of sows are removed due to old age
(see Table 1.) In addition, 11% are removed due to poor performance, mainly due to small litters at birth and weaning (7%). ”Unplanned removal” includes removal of sows due to reasons such as reproductive failure, lameness and mortality. It is this unplanned removal that presents the greatest challenge for commercial pork producers since it accounts for almost 70% of the removals on American breeding farms. The most common removal reason is reproductive failure, which accounts for 32% of the removals. Most of these are culled due to return to estrus (17%) but lack of heat also is a commonly reported reason (8%). Locomotor disorders were another common unplanned removal reason, which accounted for 14% of the removals. This includes
lameness (10%) and “downer” sows (4%).

    The proportion of different removal reasons varies with removal parity number. Unplanned removal accounts for most of the removal in low parity numbers. The proportion of removal due to reproductive failure (e.g. return
to estrus, lack of estrus) is almost 50% in parity one and decreases as parity increases. Reproductive failure represents the largest removal reason up to parity 5, where it accounts for 30% of the removals. Removal due to locomotor disorders mainly occurs in parities 1-5, whereas removal due to low productivity mainly occurs after parity 3. Removal due to old
age is the most common removal reason after parity 6.

   Today, sow removal from the breeding herd of commercial operations includes a substantial proportion of sows that are not sent to slaughter. These sows are mortalities or are euthanized on the farm. Figure 2 shows that of
the removed sows, 84% were sent to slaughter, 3% were euthanized on the farm and 12% were mortalities found on farm. Sows that are sent to slaughter represent a relatively small income due to cull sow value to the operation, but it is better than the zero-value alternatives of mortality or euthanization. In addition, the proportion of sow mortality is highest in low parity
numbers. This is, therefore, the worst kind of removal, both in terms of economics and animal well-being.
    Every farm is unique, with differing housing and management practices that may result in a specific removal pattern for each farm, and variation between farms is large. In the analyzed data, the average removal parity ranged from 2.7 to 7.1 and the proportion of removed sows sent to slaughter ranged from 57% to 99% between farms. The removal pattern reflects the farm’s status and by analyzing the data, it is possible to find weak points to improve. For example, a farm with lameness problems should pay attention to feet and leg soundness when selecting replacement gilts, and floor surfaces throughout the breeding, gestation and farrowing areas should be evaluated. On the other hand, a farm with high removal rates due to reproductive failure should closely monitor management of the sow around the breeding phase. It is important that sows are bred at the correct time and that high quality semen is used.


The biggest challenge is that not enough sows reach the later parities. A too-hig
proportion (30%) of sow removals occurs before the sows reach parity 3. This means
that almost every third sow has a negative net income. These figures don’t even include
the costs associated with gilts that are removed before their first litter, since the
analyzed data only includes sows with at least one litter.
   Reduction of sow removal could be accomplished by improving management,
breeding for more robust sows or by making systems more adaptable to the sows. In
addition, it would be possible to reduce high removal rates by simply accepting a single
bad litter or a single return to estrus without removing the sow.
   Another way to reduce a part of the high early removal is by increasing selection and
removal among gilts. If there is little or no selection before first parity, it may cause a
negative spiral where sows are replaced by gilts that only get one litter and then new
gilts have to be purchased, and so on. The result of this is a lower parity distribution on
the farm, which is more likely to result in lower productivity and give rise to a higher
proportion of reproductive problems.
   Gilts should not replace a sow unless the sow is in a poor physical state or is at a
poor productivity level where the replacement gilt is expected to be more productive.
Remember, sows on average have larger litters than gilts. In addition, that mediocre gilt
is likely to be a mediocre sow (i.e., a selected gilt with poor feet and legs is likely to be a
sow with even poorer feet and legs). Select gilts with good legs and good reproductive
performance. Scientific studies have shown that gilts that reach puberty at a later age
are likely to have a shorter productive life (Koketsu et al., 1999; Schukken et al., 1994)
and are more likely to be removed due to infertility (Schukken et al., 1994). Also, sows
that are older in age when they farrow their first litter have a higher removal risk during
their productive lifetime, compared to sows that farrow their first litter at a younger age
(Engblom et al., 2008; Serenius and Stalder, 2007).
    In conclusion, breed only gilts with good early indicators of reproductive
performance and send the mediocre gilts to slaughter where they have a greater value
per pound of live weight when compared to cull sows and their corresponding value.
An operation that has a greater proportion of sows producing until the later parities is
likely to improve parity distribution on the farm, which improves production results. It
is economically favorable to occasionally rebreed a sow instead of replacing her with a
gilt. Typically, a sow returning to estrus can be rebred twice for less money than it costs
to rear or buy a gilt. So if you have the choice, send a mediocre gilt to slaughter and save
yourself some money by giving a sow a second chance!

Editor’s Note: Linda Engblom, PhD, is a post-doctorate research associate at Iowa State University. She is from Sweden and has studied sow removal and sow longevity there. Ken Stalder, PhD; and John Mabry, PhD. are in the Department of Animal Science at Iowa State University, Ames, IA. For more information or comments, contact: lengblom@iastate. edu.
For references in this article and more information, go to: www.swine.farms.com

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