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High and Low Sow Longevity

High replacement rates for first- (P1) and second-parity (P2) sows have skewed current parity structures on most sow farms towards younger, less productive females. As a result, herd productivity is being limited because females are culled before they reach their peak periods of reproductive performance.

Teasing apart all the potential causes of reduced sow longevity is challenging, since many factors could be involved. One of the first steps would be to compare normal management practices between farms that differ in sow longevity.

Results presented in this report involve a commercial production system consisting of two 2,400-head commercial sow farms that receive replacement gilts from the same multiplication flow, yet differ considerably in terms of sow longevity. The high-longevity (HL) farm typically has 26% of its sows reach a sixth parity, while the low longevity (LL) farm usually only has 12% of its sows farrow six litters.

A total of 1,600 gilts were tagged at birth and monitored through the multiplication phase. In most cases, littermates were sent to either the HL or LL farms. Upon arrival at the two commercial farms, routine management of the sows is solely at the discretion of the farm personnel, and they make all feeding, breeding and culling decisions. A variety of information such as weight and body condition changes, feed intake and mating quality scores is being collected, in addition to routine management and environmental data. Finally, when females were removed from production on either farm, their reproductive tracts are being evaluated.

At present, sows have been rebred following their second lactation (Parity 2). Although the results are preliminary, there are some interesting trends when comparing the HL and LL herds.

After sows were rebred following their first lactation, the HL farm still had 78% of the gilts remaining in production, while the LL farm only had 58%. The majority of this difference can be attributed to the proportion of gilts that were bred and entered into production — which added up to 98% of the gilts on the HL farm, compared with only 83% of their contemporaries on the LL farm.


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Farrowing rates for P1 sows were comparable for the two farms. There was only a 4% loss of sows from weaning to rebreeding on the HL farm, compared with a 12% loss over the same period for the LL farm. This trend has continued during the rebreeding of sows following their second lactation.

Specific management activities at different stages of production are outlined in Table 1. While the manner in which these data are being collected does not allow for the establishment of cause-and-effect relationships, it does illustrate some interesting associations between specific management practices and sow longevity.

First, there are differences in the type of boars used for estrus detection and management. The HL farm uses a younger boar and collects heat check boars periodically, while the LL farm uses older boars that aren’t collected. This difference appears to be associated with increased libido of the heat check boars and enhanced standing reflexes for both sows and gilts on the HL farm. Most of the gilts that were delivered to the LL farm, but were never bred, had corpora lutea or corpora albicantia on their ovaries at the slaughter check. This indicates that they did ovulate at some point, and presumably their estrus was not detected.

One of the unique differences in how gilts are managed between the two farms is that on the HL farm a single person is responsible for breeding all the gilts and then moving them after breeding into their gestation stalls. On the LL farm, these tasks are performed by different members of the breeding barn staff as the need arises. During our daily observations of routine activities, there weren’t any obvious differences among the two farms in how the gilts responded to the farm staff while they were being moved. However, on the HL farm, movement of gilts from breeding to gestation took less time, and there were almost no incidences where gilts tried to escape from their handler while being moved. The significance of these observations remains to be seen, but it is tempting to speculate that if they are representative of animals that are calmer while being handled by workers, then this could have benefits not only in breeding but during farrowing and lactation as well.

Sows are assisted during farrowing on the HL sow farm fairly aggressively, compared with the LL sow farm. It is interesting to note that the HL sow farm has fewer sows with retained placentae and dead piglets, and fewer sows that experience transient decreases in feed intake, which were defined as a two- to four-day period of either not eating or having a reduced appetite.

From a physiological perspective, it is reasonable to expect that sows with retained piglets would experience discomfort and increased body temperatures, which could result in transient reductions in lactational feed intake. From a management perspective, the timely assistance of sows during farrowing should decrease the incidence of retained piglets. Hence, it seems plausible that there are direct relationships among these three parameters.

Surprisingly, there really were no statistical differences in weight loss and body condition changes between the two farms during the first two lactations. The first lactation is typically viewed as the biggest hurdle for sows to overcome if they are to remain in production, and rather large differences between the two farms were expected. These data should not be interpreted as evidence that feed intake during lactation does not affect sow longevity. It has been well documented that the exact opposite is true. Failure to find differences in these two areas probably means that both farms do a commendable job feeding sows, so that they don’t lose excessive body condition during lactation; and having accomplished this, there obviously are other management factors that become important and influence sow longevity.

At the beginning of the second parity, there was a 20% difference in the proportion of sows still in production, which is about the same margin that normally is observed between these two farms in the proportion of sows that farrow six parities. Consequently, it appears that the periods of management of gilts from delivery to breeding, and then during their first lactation, are critical for the sow longevity identified in this production system thus far.

Some of the main differences between these two farms with historically good and poor sow longevity involve detection of estrus and assisting sows during farrowing. Consequently, these may be areas that deserve more attention on farms wanting to improve sow longevity.

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