Heavy doses of fiber curb appetite and improve welfare of gestating sows.

Hungry, pregnant females often display certain stereotypic behaviors that suggest frustration and an elevated desire to eat.

Keeping them content with heavy doses of dietary fiber may be the answer to curbing hunger pangs and improving welfare, says a University of Minnesota-Morris swine nutritionist who studied the actions and postures of gestating sows to measure the correlation between behavior and feeding motivation.

Studies have listed stereotypical behaviors as motions that are repeated regularly, serve no obvious function and are useless to the animal, explained Lee Johnston at the Minnesota Nutrition Conference in St. Paul last fall.

These behaviors can include, but are not limited to bar biting, sham or vacuum chewing (chewing motion that is not associated with feeding) and nosing or licking the floor or feeder when feed is not present.

In addition, time spent standing and/or active, as opposed to resting, is used to indicate hunger because sows do not appear satisfied, Johnston added.

“The sow is a lightening rod for welfare questions. The occurrence of undesirable stereotypic behaviors is often used to measure sow welfare. They are limit-fed and hungry, and it causes an increase in unnatural behaviors,” he pointed out. “We'd like to see sows resting more, so we looked at treating the symptom by changing the diet.”

An obvious approach to reducing hunger and the associated stereotypes is to offer pregnant sows more feed. Unfortunately, this approach also supports excessive maternal weight gain during pregnancy, which could cause sows to back off feed during lactation and impact sow longevity. Higher feeding levels also result in larger sows that do not easily fit in their existing accommodations.

Soluble Fiber Preferred

Johnston prefers ingredients that contain high levels of soluble fiber vs. insoluble fiber. Soluble fiber has a higher nutritional value that's more readily fermented in the gastrointestinal tract of sows and is more effective in improving their welfare, he said.

Fermentation increases production of short-chain fatty acids, which are readily absorbed through the intestinal wall into blood. These fatty acids are available as an energy source for a sustained period after each meal.

In fact, diets containing very high levels of fibrous feed ingredients can be just as digestible as high-starch diets for gestating sows, Johnston explained.

Shredded beet pulp has consistently shown positive effects on sow behavior. It is high in soluble fiber highly fermented by sows. Johnston advised against pelleted pulp.

The diets listed in Table 1 are targeted at achieving 30% neutral detergent fiber (NDF), which is a rather high level of fiber, Johnston noted.

“This level of fiber seems necessary to significantly reduce stereotypic behaviors. Unfortunately, some of these diets will have difficulty flowing through our typical commercial feed handling systems,” he said.

The beneficial effects of high-fiber diets will only be realized if the sow's nutrient requirements for maintenance, growth and reproduction are met. In other words, the data indicates there is one level of nutrient/feed intake to support acceptable reproductive performance and a higher level for improved sow welfare.

Set in Their Ways

“Stereotypic behaviors increase as sows age, and high-fiber diets become less effective in reducing behaviors in older sows,” Johnston said. They develop a consistent repertoire of behaviors, including stereotypic behaviors that are elicited by feeding. Regardless of diet composition, sows express these behaviors when fed. Back in 1993, a team of researchers referred to this phenomenon as “channeling” of behaviors, he added.

In an effort to see if feeding management influences behaviors, sows were offered two meals per day instead of one. The theory was a second feeding would reduce a sow's need to exhibit the stereotypic behaviors.

Unfortunately, the time sows spent expressing the behaviors actually increased, reported Johnston. “We just got them excited twice a day instead of once.” So regardless of fiber content, frequent feeding is not likely to reduce behaviors in sows that already display abnormal activity.

Johnston felt, however, that more frequent feeding may reduce development of stereotypic behaviors in young sows.

The balance of evidence suggests that diets high in fiber will reduce stereotypic behaviors in sows and increase their level of satiation, he said. Currently, the assumption is that a decline in stereotypic behaviors equates to an improvement in welfare of the sow.

“The main message is that fiber is good for gestating sows; however, it will take very high levels to significantly reduce stereotypic behaviors. We need to work on additional approaches, probably using fiber and other ingredients to control these undesirable behaviors and their underlying causes,” he said.

Johnston offered these tips to minimize stereotypic behavior in a commercial system:

  • Provide diets containing over 30% NDF;

  • Provide high soluble/fermentable fiber;

  • Ensure maintenance, growth and reproductive requirements are met, and

  • Feed in meal form vs. pellets; it takes longer for sows to eat. Mash feed is good.

Table 1. Samples of Diets that Contain Over 30% NDF and the Nutrients They Provide
lb./ton Corn-SBM Soy Hulls Beet Pulp DDGS
Corn 1,635 1,081 815 850
Soybean meal 280 100 125 75
Soy hulls 750
DDGS 1,000
Beet pulp 1,000
Dical/phos 45 43 40 25
Limestone 20 6 30
Salt 10 10 10 10
Vit./minerals 10 10 10 10
Diet properties
ME, kcal/lb. 1,478 1,270 1,293 1,573
Lysine, % 0.63 0.52 0.55 0.67
NDF, % 8.6 30.4 31.2 26.1
ADF, % 3.2 20.6 18.1 10.5
ME = metabolizable energy; NDF=neutral detergent fiber; ADF=acid detergent fiber; DDGS=distiller's dried grains with solubles