The NAHMS Survey on Sow and Gilt Management

Livestock Update, July 2002

Allen Harper, Extension Animal Scientist ­ Swine, Tidewater AREC

Last month this report provided a summary of the recent USDA National Animal Health Monitoring System's (NAHMS) study on current nursery pig management practices on U.S. hog farms. This same NAHMS study also presented survey snapshots of other categories of swine production including sow and gilt management, farrowing and weaning productivity, grower-finisher pig productivity, and bio-security and disease prevention practices. One particular area of swine production that has changed rapidly in recent years is management of the breeding herd. The following is an outline of the NAHMS Swine 2000 study findings in regard to breeding sow and gilt management on todayıs hog farms. For those who wish to study the full NAHMS report, it can be found on the internet at http://www.aphis.usda.gov:80/vs/ceah/cahm/Swine/swine.htm.

Proportion of Hog Farm Sites Maintaining a Breeding Herd. The study indicated that overall, only about half (53%) of hog farm sites surveyed maintained a breeding herd and gestation and farrowing facilities. Although there was no historical data presented to compare this value to, it does reflect the trend in swine production away from traditional farrow-to-finish farms and toward hog farms that specialize in specific phases of production. Certainly farrow-to-finish sites still exist today, but farrow-to-wean or farrow-to-feeder pig farms that send pigs to separate nursery or finisher farms are now commonplace in the industry.

Mating Techniques. Pen mating in which sows and boars are penned together such that exact breeding dates and number of matings per female is unknown to the herdsman, continues to be practiced on hog farms. However, the survey indicated that this breeding method is used much more on smaller hog farms (less than 250 sows) than on large farms (500 or more sows). Pen mating was used on 65% of small farms whereas less than 1% of the large farm category used the pen mating technique. For moderate sized breeding farms (250 to 499 sows), pen mating was practiced on 11% of the sites. On all sites, 51% of sows are bred twice during a given heat period. Only 6 % are bred once, 26% are bred three times and it is unknown how many matings occur during a heat cycle for 17% of females. This latter figure reflects the unknown mating frequency that occurs in pen mating systems used primarily on small hog farms.

Use of Artificial Insemination. Use of artificial insemination as a primary breeding method continues to increase on sow farms. For large hog farms, 85% performed artificial insemination for both a first and second mating during a sow heat period. Another 9% of large farm sites used hand mating for an initial mating followed by an artificial mating during the heat period. For moderate sized farms, 51% used artificial insemination exclusively and 7% used a combination of hand mating and artificial insemination. Artificial insemination was used exclusively on only 15 % of small farms and less than 2% of small farms used a combination of hand mating and artificial insemination. For all sites combined 65% used artificial insemination exclusively and 7% used a combination of hand mating and artificial insemination.

The continued expansion of use of artificial insemination (A.I.), especially on moderate to large sized farms, reflects continued refinements in A.I. techniques, fresh semen extenders, A.I. breeding products, semen delivery and the recognition that genetic improvement and consistency can be enhanced with use of A.I. Furthermore, it has been demonstrated that time and labor requirements in the breeding barn are actually reduced when using A.I. compared to hand mating if a substantial number of sows must be bred on a weekly basis. The survey indicated that on farms practicing A.I., 17% collected and extended semen from boars on site, 21% used semen collected at their own boar studs at a separate site and 73% used semen purchased from commercial boar studs. Apparently some sites obtained semen from more than one source because the percentage data in this part of the survey sums to more than 100%.

Sow Culling and Death Losses. Culling and death rates continue to be sited as problem in the swine industry. The NAHMS survey did indicate that sow losses due to culling or death losses are a legitimate concern for the industry, but they do not appear as high as sometimes indicated on individual problem farms. Overall the survey indicated that the percentage of sows culled over a 6 month period was 17% and the death loss of sows in inventory during that period was 3%. Losses were slightly greater on larger farms with an 18% cull rate and 4% death loss compared to smaller farms with a 15% cull rate and 3% death loss. Of the females culled, the survey indicated the reasons for culling in order of magnitude were: age 42%, reproductive failure 21%, lameness 16%, performance 12% and other reasons 9%.

Introduction of Gilts and Breeding Males into the Herd. The method of bringing new replacement gilts into a herd is important because it has a major bearing on herd bio-security and disease prevention. On large farm sites 69% always isolated or quarantined new gilts before exposing them to the existing herd. Also on large farm sites 7% sometimes isolated new gilts, 14% never isolated new gilts and 10% produced replacements on site and never had new gilt arrivals. For small hog farms, 26% always isolated new replacement gilts, 8% sometimes isolated new gilts, 17% never isolated new gilts and 49% produced replacements on the farm and never had new gilt arrivals.

For new boar placements on large farms, 67% always isolated new stock, 5% sometimes isolated, 13% never isolated and 15% had no new arrivals for isolation. On small farms, 53% always isolated new boars, 12% sometimes isolated, 21% never isolated and 14% had no new arrivals for isolation.

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