To maximize your number of pigs per litter and to ensure that each sow has a long, productive life, proper nutrition during gestation is critical. Determining each sow’s feed requirement during this important development stage can have major effects at farrowing and beyond.

Basically, there are three objectives in providing proper gestation-diet levels:

  • To get the sow in proper body condition for farrowing.
  • To maximize both the farrowing rate and litter size.
  • To meet the sow’s daily nutrient  requirement at the lowest possible cost.

Ensuring that each female gets her full daily allocation of feed takes careful observation, and knowledgeable barn workers are an important asset. In group-feeding situations, it is especially important to take extra care to see that each animal gets its fair dietary share.

Ideal body condition at farrowing is the goal, as over-conditioning can lead to mammary development problems and reduced feed intake during lactation. Not enough conditioning can result in lowered reproductive performance and other physical challenges such as shoulder sores.

By recording two key measurements — bodyweight and backfat — you can make good progress on your gestation feeding levels.

Bodyweight:To set feeding levels, start by estimating the bodyweight on a high percentage of your sows. Bodyweight can be measured conveniently with a tape measure developed by Kansas State University swine researchers. (See sidebar.) The researchers offer this advice: “Once the base feeding level is set, the daily feed requirement for sows to maintain bodyweight increases by 0.3 pounds for every 50-pound increase in the sow’s weight.” This applies to sows fed a corn/soybean meal diet.

Backfat:Using a bodyweight estimate alone to determine a sow’s optimum body condition for farrowing can have drawbacks and yield inaccurate conclusions. By evaluating backfat depth, along with a sow’s bodyweight, you can more accurately determine proper feeding levels. When considered together, the two measurements provide a clearer picture of feed requirements.

Mike Tokach, swine nutritionist at Kansas State, offers this perspective: “At farrowing, you want to have as few sows as possible with less than 15 mm or more than 21 mm backfat depth as measured at the animal’s last rib.”

Knowing the sow’s estimated bodyweight and backfat depth at breeding and the targets at farrowing tell you whether feeding adjustments are necessary. For example, if you want to add backfat, the daily feed requirement during gestation goes up by 0.4 pounds to 0.5 pounds for every 3 mm in desired backfat gain.

Also, look for uniformity in backfat thickness within your sow herd. “If more than 75 percent of the sows are between 15 mm and 21 mm at farrowing, you are doing a good job of setting gestation feeding levels,” according to Tokach.

Once you have estimated bodyweight and measured backfat thickness, aim for feeding levels recommended by Kansas State researchers presented in the accompanying table. If the diets that you are now feeding are higher or lower than 1,500 kcal of metabolizable energy per pound, you will have to customize the feeding levels. For example, if the diet you are feeding provides only 1,350 kcal of metabolizable energy per pound, you will have to increase the amount suggested by 10 percent.

Check the backfat measurement at a key gestation stage. At seven weeks after mating, sows that appear very thin should actually be scanned to get a clear measure of the backfat levels. “You could check 10 percent to 15 percent of the females at this time,” Tokach says. “If sows are not at the desired backfat depth, you should work to increase individual feed intake by 1 pound per day.”

Watch water intake.Inadequate water consumption can reduce feed intake and is another factor to guard against. As in all pork production phases, clean, fresh water must be available to gestating sows at all times. Common problems that may cause inadequate water intake are plugged drinker nipples, poorly functioning water troughs and inadequate water pressure.

Glen Almond, DVM, North Carolina State University College of Veterinary Medicine, estimates that gestation sows require 3 gallons to 6 gallons of water per day. Since factors such as ambient temperature, number of animals per pen, type of housing and general health condition can all influence water intake, close scrutiny is needed to ensure sows are consuming adequate amounts of water.

Almond suggests checking nipple flow rates often and testing them before placing animals in a pen. He also points out that in high ambient temperatures, sows will drink almost twice the amount of cool water (50° F) than warm water (80° F).

As fetal gain increases in late-gestation, it is important to increase the feeding level to meet the sow’s maintenance needs and provide for the corresponding uterine gain. Increase feeding levels by 1 pound to 2 pounds per day during the last two weeks of gestation to meet the sow’s growing needs, suggest Kansas State researchers.

Other variables also bear watching. Dietary amino acid requirements vary based on expected lean-tissue gain during gestation. “A mature sow gaining 45 pounds from breeding to farrowing requires less than 9 grams per day of lysine,” according to Kansas State researchers.  “However, younger gilts bred at 285 pounds with an expected weight gain of 65 pounds would require 13 grams of lysine per day.” If the target weight increases, the amino acid requirements also increase. This is another area where stepping up the late-gestation feeding levels will help meet the animal’s rising amino acid needs.

 If you implement parity segregation, two different gestation diets can be used — one for sows at the 9-gram level and one for gilts at the 13-gram level.

This practice would help avoid over-feeding sows as you attempt to meet the gilts’

lysine requirements.

By calculating and recording the sow’s bodyweight and backfat, you can better customize your gestation feeding program to more accurately accommodate each animal’s needs. That not only will make your feeding program more economically efficient, it also will improve your herd’s reproductive performance — both of which measure up to greater success.

Calculate Backfat and Bodyweight

Backfat depth and bodyweight should both be considered when determining gestating sows’ feed requirements.

You can estimate a sow’s weight by taking flank measurements with a vinyl tape developed by Kansas State University swine nutritionists. The tape is divided into color-coded sections with each section corresponding to a weight group.

The Kansas State team recommends that the measurement be made right in front of the sow´s back legs. Run the tape from the point of one flank, over the sow’s back on to the point of the other flank.

The K-State Sow Weight Tape is available for $5 per tape by calling (785) 532-1267 or e-mailing 

The Kansas State Extension swine nutrition team recommends scanning sow backfat levels at breeding. The measurement provides an excellent guide in determining gestation feeding levels required for optimum condition at farrowing. Ultrasound measurement should be made at the last rib, approximately 4 inches off the midline.

“For sows whose backfat and visual evaluation do not seem to match, we recommend scanning the sow on both sides of the midline and averaging the values to determine backfat,” says Mike Tokach, swine nutritionist at Kansas State.

Once you know the weight group that a sow falls in, and its backfat depth at breeding, you can determine the appropriate feeding level by referring to the accompanying chart.

Feeding levels (pound per day) for gestating sows based on backfat and weight category at breeding*

Flank-to-flank measure
Estimated Weight (pounds)

at breeding
9-11 mm
12-14 mm
15-17 mm
Over 17 mm
Less than 36.3" Less than 325 lbs 5 lbs 4.4 lbs 3.9 lbs 3.4 lbs
36.4" to 39.2" 325 to 400 lbs 5.5 lbs 5 lbs 4.4 lbs 3.9 lbs
39.3" to 41.8" 400 to 475 lbs 5.9 lbs 5.4 lbs 4.9 lbs 4.3 lbs
41.9" to 44" 475 to 550 lbs 6.4 lbs 5.9 lbs 5.4 lbs 4.8 lbs
Greater than 44" 550 to 650 lbs 6.9 lbs 6.4 lbs 5.8 lbs 5.3 lbs

Source: Kansas State University

* Based on a diet containing 1,500 kcal metabolizable energy per pound (corn/soybean meal). Feeding level should be increased 1 pound to 2 pounds per day at day 100 of gestation.