Sow herd culling and mortality rates have reached unacceptable levels in some herds.

Reproductive failure is the most common reason sows are culled from the breeding herd.

Many of these cull sows are excessively thin after nursing a large litter, are experiencing nutritional deficiency due to poor feed intake or have other health problems. Higher replacement rates naturally increase associated costs.

Benefits Are Multifold

Economic viability of the sow herd hinges on longevity, among other factors. At $200 gilt replacement cost and $44 market price, it takes at least three parities for a sow to reach a positive net present value — that is, the point where a sow essentially pays for herself.

For a sow to remain in the herd, she must farrow, nurse and wean a large litter, then breed back within an acceptable period of time. If she falls short, then she is culled.

One important approach to reducing culling and mortality rates is to improve sow body condition during gestation. The attached poster was developed to help pork producers more effectively evaluate sow body condition, and to ensure appropriate nutrition is provided to every sow in the breeding-gestation facility.

Sow body condition is critical to the overall health, welfare and productivity of breeding herd females. Without proper nutrient management, sows can quickly fall into a state of poor reproductive performance and increased susceptibility to disease.

If a sow begins to utilize body reserves (fat used as an energy source, muscle used as a protein source), she will soon metabolize these tissues and lose body weight.

Conversely, when a sow consumes more energy than she needs for normal body maintenance and fetal development, excessive weight gain will occur. This results in wasted feed and decreased reproductive performance.

Maintaining proper body condition helps sows accomplish their reproductive tasks; therefore, it is essential that the caretakers of the sow herd have the ability to evaluate body condition.

Indicators of Body Condition

The ability to assess body condition requires both subjective (visual) and objective (measurable) evaluation of body condition indicators.

Breeding herd managers must be properly trained. Failure to do so will result in incorrect feeding levels and sows that are either too thin or too fat. Either extreme will be detrimental to sow productivity and economic efficiency.

It is important to note that assessing body condition is not limited to estimating the sow's level of backfat. Correct evaluation of body condition relies on accurately assessing a combination of weight, backfat and the lean muscle mass of each sow.

While backfat is a good indicator of the metabolic status of a sow, subjective body condition scoring alone will not determine backfat thickness and energy reserves.

An objective approach to determining body condition score was developed by Kansas State University, and is based on an estimate of weight and the measurement of backfat thickness.

Backfat estimates can be gathered using ultrasound equipment, which operates on the principle of sound waves bouncing off tissues of varying densities (skin, fat, muscle, bone).

“A-mode” ultrasound is the most common ultrasound equipment used, and the Renco Lean-Meater (Renco Corp., Minneapolis, MN) is a good example of a user-friendly tool for estimating backfat thickness. The very portable units can be operated with minimal training and a read-out is provided in millimeters of backfat thickness.

Several other A-mode machines, also used for pregnancy diagnosis, have the capability of measuring backfat depth. These dual-purpose machines are more costly, however. A-mode ultrasound does not have the capability of measuring loin muscle area.

More sophisticated, and costly, “B-mode” ultrasound equipment is also available. Often referred to as “real-time” ultrasound, these machines reflect a video-displayed, two-dimensional image to visualize fat and muscle. Many B-mode ultrasound machines utilized for pregnancy detection also have backfat thickness and loin muscle depth and area-measuring capabilities. These machines require more training to be used effectively.

Measuring Backfat

To estimate backfat thickness accurately using ultrasound, it is critical to place the transducer in the correct location consistently. The easiest location to identify is the last rib. See Figure 1 as a reference for finding the last rib.

The ultrasound operator should palpate the area near the rear flank until the last rib is found. Moving upward, the transducer should be placed 2.5 in. off the midline of the sow's spine. If A-mode ultrasound is used, it is best to take two readings, then record the highest of the two values.

Scoring Body Condition

If subjective body condition scoring is the preferred method on a farm, ultrasound should be used as a guide for training. Even an experienced stock-person can benefit from periodic training to ensure visual evaluation is accurate.

Body condition scores tend to drift slowly away from the “ideal” over a period of time. Sometimes it is valuable to have an experienced, outside observer come in to periodically evaluate sow condition. This practice is especially beneficial when new genetic lines are introduced into the sow herd.

In order to properly establish body condition scores, it is critical to understand the points of evaluation and be able to distinguish between fat and muscle.

Sows should be scored early in gestation to ensure proper feeding levels. Begin by locating the ribs, backbone and hips (or hook bones) of the sow (Figure 1). These points of the sow's body are used because the tissue between the skin and bones is fat tissue. Focus on the shoulder blades, ribs, backbone and hip bones. It is important to evaluate more than one of these areas when assessing body condition, because animals deposit fat at different degrees at different locations.

The line drawings in Figure 2 help illustrate the physical appearance of sows at different body condition scores, including the difficulty of detecting the bones at key points of the sow's body.

The photos in the attached poster provide real examples of these body condition scores. The “high” and “low” view from the rear of the sow provides visual references at each body condition score. The approximate range in backfat associated with each score serves as an additional reference.

A sow with a body condition score of “3” is considered optimum. These sows will enter the farrowing crate with adequate fat reserves to sustain them through lactation. These sows should eat and milk well, and exit the farrowing crate with a body condition score of about 2.5 at weaning.

Sows with a condition score of 1 (excessively thin) or 2 (thin), should receive additional feed in order to attain a score of 3 before they farrow.

For sows exiting farrowing in poor condition (<14 mm [0.55 in.] backfat), it may be advantageous to skip a heat cycle so they can accumulate more body reserves (backfat) before breeding.

Extremes Cause Problems

It should be every farm's goal to have no sows with a condition score of “1,” because these sows are in a compromised state of welfare and very likely will not exhibit signs of estrus. If bred, often they will not successfully maintain pregnancy.

Sows that are too thin as they enter the farrowing crate are unable to consume enough feed to both lactate and accumulate the weight gain needed for body maintenance. These sows are often in a state of energy depletion at weaning and often do not successfully return to estrus.

Sows may lose 2 to 4 mm (0.08-0.16 in.) of backfat during a lactation period, but they should not fall below 14 mm, the minimum level of reserves required for a sow to successfully rebreed.

Most reproductive hormones are made from a base of fat molecules and, therefore, body condition influences reproductive events.

A good target for sows is between 18 to 20 mm (0.70-0.78 in.) of backfat prior to farrowing. Adequate fat reserves provide the energy needed to lactate successfully.

We do not want excessively fat sows, however. Research has shown that fat sows may have difficulty farrowing, consume less feed in lactation and potentially wean lighter litters. In addition, their subsequent litter is often smaller.

Body condition should be evaluated periodically during gestation. This will prevent sows that were evaluated as too thin from becoming too fat as they receive extra feed.

Conversely, sows can become thin during gestation and require adjustments to their feed allotment.

One telltale sign that sow body condition is not being evaluated, or the scores are not being accurately utilized, is to examine the automatic feed drops in gestation. If all or a vast majority of the feeders are on the same setting, an assessment of gestation feeding management is likely warranted.

Note that backfat reserve levels will vary from farm-to-farm and among different genetic lines. Producers should consult with their genetic supplier for the recommended body reserves for sows.

Producers may find it beneficial to crate or pen sows according to body condition score to make management of sows easier.

If a significant percentage of sows fall within either of the extreme body condition scores (1 or 5), then a complete evaluation of gestation and lactation management, nutritional programs and health status should be conducted to determine the reason for the disproportionate number of low or high scores.

Finally, increasing feed and weight gain of the sow two weeks prior to farrowing goes primarily towards fetal growth and not towards body condition.

To Order More Posters

Additional copies of the “Sow Body Condition Scoring Guidelines” poster are available by contacting Newsham Genetics at 515-557-9352 or via their web site, www.Newsham.com (Click the “contact” bar to view order form). Posters are also available by calling Pork Checkoff at (800) 456-PORK.

Figure 2. Body Condition Scores of Sows
Score Condition Ease of detection: ribs, backbone, hip bones
1 Emaciated Obvious
2 Thin Easily detected with pressure
3 Ideal Barely felt with firm pressure
4 Fat None
5 Overly fat None