Feed aversion induced by intraruminal infusion with larkspur extract in cattle.

Twelve Hereford heifers were infused with larkspur extract (group 1, n = 4), lithium chloride solution (group 2, n = 4), or sodium chloride solution (group 3, n = 4). After 3 weeks of being fed basal ration (meadow grass hay), all heifers were offered a ration of alfalfa pellets (3,400 g) in a 2-phase, single-day feeding regimen. In phase 1, the amount eaten within 45 minutes was measured by weigh-back of uneaten pellets. In phase 2, cattle that ate greater than 150 g of pellets in phase 1 were offered the balance of uneaten pellets and were infused with their respective designated solution. Five pairings of pellet feedings and appropriate infusions were given at 2- or 3-day intervals to initially induce feed aversion. Heifers in groups 1 and 2 developed a strong aversion to pellets by the 5th feeding. Persistence of aversion was tested twice at weekly intervals. Infusion of cattle with larkspur extract or lithium chloride solution induced a persistent aversion to an otherwise palatable feed.