Nell goes nuts when she's kept indoors.

But when the 7-year-old border collie spied a pen of four nervous sheep in the Pavilion for Agriculture and Livestock Education arena, she got down to work.

Owner George Good swept an arc in the air with his arms, and with a "whooshing" whistle, Nell shot into the pen.

"I don't have to say a word," Good explained to an animal science class learning about companion animals Thursday afternoon.

Nell circled around him as he talked, keeping the sheep, each wearing a terrified expression, in a tight row.

Good's observers, primarily freshmen, were studying animals who help people, such as service dogs helping persons with disabilities.

Nell does the work of an uncountable number of people, said Good, manager of the animal science's sheep unit.

The class, Introductory Animal Agriculture, previously covered only animals traditionally involved with agriculture, but in recent years, they've expanded to include other creatures who help their human counterparts.

"We're recognizing more and more that the population is changing - companion animals is a growing field for work," said Associate Professor Nathalie Trottier.

Teaching assistant Fred Gingell said he took the class before working animals were included in the curriculum.

"Part of good animal husbandry is understanding different species," Gingell said. "It's good they were added because companion animals are a part of animal science."

Learning about nontraditional agriculture animals can open students to new career options, Trottier said.

"They might realize, 'maybe I want to make this a part of my life,'" she said.