Sheep Flock to New Flavors says USU Researcher

Sheep given a variety of feed flavors will stop gorging and start eating more small meals over the course of the day, says Utah State University researcher Juan Villalba. His findings, published in the August 2011 issue of the Journal of Animal Science, could help livestock producers maximize feed intake and nutrient efficiency at the same time.

Villalba authored the paper, “Feed Behavior and Performance of Lambs are Influenced by Flavor Diversity,” with Alex Bach of Spain’s Catalan Institute for Research and Advanced Studies and Ignacio Ipharraguerre of Spain’s Lucta, S.A., an animal nutrition manufacturer.

An associate research professor of foraging behavior in USU’s Department of Wildland Resources, Villalba says current sheep feeding practices usually provide animals with only one flavor of feed.

“This is like humans eating only hamburger every day,” he says. “They get tired of eating that same flavor over and over.”

In one part of the experiment, young sheep were given a choice of plain feed, sweet-flavored feed, bitter-flavored feed and umami-flavored (savory) feed. (Umani, which means “pleasant savory taste” in Japanese, is the so-called “fifth basic taste” in the basic taste quintet that includes sweet, sour, bitter and salty.)

Though all the feed types in the study had the same nutritional value, the flavors were meant to indicate the presence of certain elements. Bitterness, for example, tastes like plant toxins, sweetness indicates a high-calorie feed and umami indicates high protein content.

The growing sheep disliked the bitter feed and favored the umami feed. Previous studies that compared only plain feed and sweetened feed had shown that young sheep favor sweeter feed, but sweet feed wasn’t the favorite in Villalba’s study. He says it probably doesn’t indicate that sheep dislike sweet feed; they may just like umami feed more.

“That reference for protein is more relevant to growing animals,” he says.

By measuring feed intake, the researchers discovered that offering a variety of food helps animals continue eating throughout the day. Instead of gorging on one type of food at the very beginning of the feeding period, the animals switched between flavors and came back for more meals throughout the day. Not only did this behavior increase feed intake, it kept ruminal pH from fluctuating.

Stable pH is important, Villalba says, because an increase in acid from eating too much starchy feed can lead to damage of rumen and abscesses in the liver.

“You won’t find those peaks and valleys in pH that you typically see in animals fed in feedlots,” he says.

Pacing feed intake could also help animals process the nutrients more efficiently, Villalba says. Producers could apply these findings in their own flocks. He suggests mixing umami flavor into feed at different ratios.

“Producers do not need to increase feed rations,” he says. “Flavors can also satiate the animal, not just nutrition.”

The desire to eat a variety of flavors is actually an evolutionary advantage. In the wild, and in some pastures today, sheep encounter many kinds of plants. By eating different plants, Villalba says, sheep can get a variety of nutrients as well as minimize exposure to any plant-specific toxins.

“Ruminants didn’t evolve in an environment where they had just one food to eat all the time,” he says.

Villalba and his colleagues noted that sheep given a variety of flavors at an early age were more willing to accept changes in feed later in life. This is good news, he says, for producers who want to switch feed types without reducing intake.

Villaba’s study was supported by grants from Lucta S.A. in Montornés del Vallés, Spain, and the USU-based Utah Agricultural Experiment Station.

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Contact: Juan Villalba, 435-797-2539, juan.villalba@usu.edu

Writer: Madeline McCurry-Schmidt, American Society of Animal Science, 217-239-3323, ext. 121; MadelineMS@assochq.org