They used to lose three-fourths of their newborn calves each year.

VOA: special.2009.11.03

And they did that by intentionally infecting calves, by harvesting their skin when they were at a certain point of the disease, and by isolating the virus from the skin of the calves.

他们有意感染很多小牛,当小牛疾病发展到一定程度,就收割牛皮,然后把病毒从牛皮里分离出来

耶鲁公开课 - 生物医学工程探索课程节选

The imported cows have given birth to their first calves.

VOA: special.2011.05.24

Calves are roped and tied in a matter of seconds.

VOA: standard.2010.01.25