Pigs are not known for being picky - 'eats like a pig' is not a colloquial metaphor, they are messy and eat everything - but new research shows they avoid bitter tastes when they can.

In a new study of nursery pig diets, researchers offered pigs different amounts of soybean meal, napus canola meal and juncea canola meal. They found that pigs ate more soybean meal when given a choice. Of course, they choose to eat everything. They're pigs. 

Napus canola meal and juncea canola meal come from rapeseed and mustard greens, respectively. Canola meals are less expensive than soybean meal. If producers can replace soybean meal in swine diets, they could produce pork at a lower cost.

In a presentation at the 2013 ADSA Midwest Branch / ASAS Midwestern Section Meeting, Dr. Jose Luis Landero from the University of Alberta  said previous studies showed that producers can replace up to 20 percent of soybean meal with napus canola meal without affecting pig performance.

Landero said the drawback to using canola meals is that the feeds naturally contain more glucosinolates. Glucosinolates are organic compounds that can cause a bitter taste. Brussels sprouts are high in glucosinolates, for example. A high level of glucosinolates in swine feed could cause swine to eat less.

In recent feeding trials, Landero and fellow researchers set up pens with two feeders. In the first trial, one feeder had a commercial soybean meal diet, and the other feeder had a percentage of napus or juncea canola meal to replace the soybean meal. In the second trial, the control feeder had neither soybean or canola meals, and the test feeder can some percentage of the three meals.

The researchers tested 360 pigs overall. They measured feed preference by dividing the feed intake of the test diet with total feed intake per pen.

According to Landero, the data showed a clear preference for soybean meal over napus or juncea canola meal. Juncea meal was the least favorite choice. Landero hypothesized that that was because juncea canola meal contains different types of bitter glucosinolates.

Landero warned scientists and producers to be careful about interpreting feed preferences. Pigs do not normally get a choice of feed, so they would probably still eat a diet with a low level of napus or juncea canola meal.