Managing Sows In Gestation

Sow herd management is generally broken into the three phases of a sow's life — gestating a litter, nursing a litter and not pregnant but getting ready for the next litter.

The longest of the three phases — gestation — could arguably be the most critical phase. In the very early stages of pregnancy, between Days 11 and 12 after ovulation, the fertilized eggs produce estradiol, a hormone that is critical to the recognition of pregnancy. Within the next two to six days, the new fetuses will attach to the uterine wall of the sow, and the placenta is formed to provide a metabolic exchange between the fetuses and the sow.

The placenta is a transitional endocrine organ that produces hormones and is responsible for maintaining the pregnancy, stimulates the maternal mammary glands and promotes the growth and development of the new litter. From start to finish, this process known as gestation takes roughly three months, three weeks and three days. Toward the end of gestation, 2-3 weeks before the litter is born, fetal growth is accelerated, putting greater physiological and nutrient demands on their mother.

It is this phase of pork production — managing sows in gestation to maximize reproductive prolificacy — that this 42nd edition in the Blueprint series is devoted to.

Gestation Management

Central to managing gestation effectively is the proper care and feeding of sows and gilts. Done well, females will remain productive through numerous parities. Poor management in this critical stage will result in high sow culling rates and excessive mortalities.

One of the tools pork producers and veterinary consultants use to guide sow management is evaluating body condition when sows are weaned, and at regular intervals throughout the gestation period. Between pages 6 and 7, you will find a special “Sow Body Condition Scoring Guidelines” poster to help managers and employees in evaluating sow condition.

Supplementing the poster, an adjoining article elaborates on the indicators of sow body condition, outlines methods for measuring weight and backfat, and presents guidelines for utilizing body condition scores in the feeding and management of gestating sows.

Additional articles follow with more detailed discussions on sow housing alternatives, nutrient management for improved condition and productivity, and the health care and maintenance of gestating sows.

A percentage of sows in any breeding herd will fail. Some will be culled voluntarily for poor prolificacy or poor disposition. Others will be culled involuntarily — most commonly for reproductive failure. A few sows will die.

In an effort to get a better handle on why sows are culled, Iowa State University researchers, funded by Pork Checkoff, investigated the physical and reproductive condition of over 3,000 culled sows delivered to two midwestern packers. Their report begins on page 28.

All sows are eventually culled, of course. Closing this Blueprint edition, the final article discusses the cull sow market and reviews management and economic parameters producers should consider in an effort to optimize the value of those cull sows.

Sow Culling Benchmarks

Several metrics serve as indicators of a sow herd's success or failure — farrowing rate, pigs born alive/litter, mummified and/or stillborn pig rates, average sow parity, pigs weaned/mated female/year, sow culling rate and sow mortality rate. All can be used to measure success or failure, but the latter three are most often quoted.

The 2004 year-end PigChamp report shows farrowing rate averaging 77.7% on the 225 farms in the benchmarking database (Table 1). A closer look at the upper and lower 10 percentile reinforces the significant differences in death rate and culling rate. On average, the database reports death rates at nearly 8% and culling rates pushing 44%. In pigs, the difference between the upper and lower 10% averages 5.5 pigs/mated female/year.

Turning to another dataset from Swine Management Services, Fremont, NE, Table 2 shows data from 150 farms out of their benchmarking database of 225 farms. Farms that were expanding, depopulating, repopulating or starting up were dropped from the dataset. Farm size ranged from 300 sows to 11,000 sows. The most recent 52 weeks of data from each farm was used, which represents 289,217 sows.

The pigs weaned/mated female/year (PW/MF/Y) figure is used as a standard metric because farms differ in the way they enter gilts into their production records.

Figure 1 shows the distribution of farms falling between 17.5 and 27.0 PW/MF/Y. The productivity of the 150 farms displays a typical bell-shaped curve. However, when culling and death loss levels are expressed as a percentage and related to PW/MF/Y (Figure 2), sow culling trends do not differ, notes SMS's Ron Ketchem. “This leads us to think there are several variables that affect sow culling decisions that may not be under the control of management, such as cull sow price, flow of replacement gilts, age and repair of facilities, etc. (However), the trend for mated female death loss shows a slight drop as farms increase PW/MF/Y. This suggests that the top-producing farms are doing a better job of finding and treating the health-challenged animals.”

Looking at culling rate only (not shown), the range from 15% up to 80% is noteworthy. Likewise, sow death loss ranges from 3% up to 19%, reinforces that stockmanship and finding and treating health-challenged females has a big impact on productivity.

Benchmarking data offers industry guidelines, but genetics, management and herd health play a large role in lifetime productivity.