Beef Cattle, Goats, Livestock, Sheep Regain Genetic Parasite Resistance Chip Hines April 24, 2017 What is the first line of defense when parasites attack livestock? A drug (chemical) is immediately purchased and applied to the animal. Does it work? Yes, it usually does. For how long? Days, weeks, All the grazing management tips you need Subscribe to read this article and over 2,500 more! Subscribe today! If you're already a subscriber, log in here.