Propping Up Farrowing Rates

There are three main variables that impact the success of a mating/service – the female to be bred (sow/gilt), semen quality, and the capabilities of the person responsible for the insemination.

There are three main variables that impact the success of a mating/service – the female to be bred (sow/gilt), semen quality, and the capabilities of the person responsible for the insemination.

Farrowing rate is one of the Key Performance Indicators (KPI’s) used in the Swine Management Services’ (SMS) database. It also has one of the flattest KPI bell curves (Chart 1) in the database. Farms vary from below 70% to 92% farrowing rate for the most current 52 weeks in the database.

Chart 2 shows the wean-to-1st service interval for the last 52 weeks, showing an average of 7.03 days and a range of less than 4 days to 10+ days. As pig weaning age goes up and more lactation feed is fed, there is a trend for weaned sows to cycle sooner.

Chart 3 shows farrowing interval – the days from one farrowing to the next. Farrowing interval is affected by lactation length, wean-to-1st service interval, days to finding open (recycling) females, farrowing rate, and gestation length. This trait varies from 138 days to 154 days, with database average of 145.6 days.

Sow fertility measures are affected by wean-to-1st service interval and percent of sows bred back by Day 7 after weaning. Fertility variables include age and weight at first breeding for gilts, sow parity, type of facility, genetics, season of the year, feed intake before and after weaning, body condition, access to water, supplemental cooling, ventilation, estrous detection and insemination technician capabilities.

Wean-to-1st service interval is a driver for improving farrowing rate and increasing litter size on the subsequent litter. The sooner a weaned female returns to heat, the more fertile she is and the more eggs are shed to improve litter size. The sow’s body condition going into farrowing, her feed intake during lactation, and feed intake after weaning influences how quickly she recovers from the farrowing and lactation process and comes back into heat.

Focus on Feed Intake
Management tips for feeding sows:

  • Sows are individuals. When and how much they eat varies. Some sows prefer to eat at night, while others favor eating during the day. If you watch Parity 1 females, most eat small amounts several times a day vs. older parity sows, which are more inclined to eat several pounds of feed once or twice a day.

  • Feed delivery systems affect feed intake. Many farms are changing how they feed sows. Rather than feeding once or twice, daily, many are hand-feeding several times per day (3-5), installing automated systems that can drop feed several times during a 24-hour period, or installing feeders with feed reservoirs so sows can have access to feed 24 hours a day.

  • Measuring feed intake (disappearance). To calculate lactation feed intake, total the lactation feed delivered to the farm during a specific period (i.e. 4 weeks; 13 weeks) then divide by the total number of lactation days in the period. Keep in mind, this calculation measures feed disappearance, not necessarily feed intake. It is important to check for feed wastage under the feeders and/or feed removed due to spoilage. It not uncommon for farms to waste 10% of the feed delivered. For a 20-day average lactation length, feed consumption should be 14-16 lb./day.
Feeding sows in lactation is an art. You must treat each sow as an individual. Her daily feed needs and her eating habits must be recognized. We feel it is important that feed be available 24 hours a day during lactation.

Key Performance Indicators

Tables 1 and 2 (below) provide 52-week and 13-week rolling averages for key performance indicators (KPI) of breeding herd performance. These tables reflect the most current quarterly data available and are presented with each column. The KPI’s can be used as general guidelines to measure the productivity of your herd compared to the top 10% and top 25% of farms, the average performance for all farms, and the bottom 25% of farms in the SMS database.

If you have questions or comments about these columns, or if you have a specific performance measurement that you would like to see benchmarked in our database, please address them to: or

Click to view graphs.

Mark Rix and Ron Ketchem
Swine Management Services LLC