Food aversion learning in sheep: persistence of conditioned taste aversions to palatable shrubs (Cercocarpus montanus and Amelanchier alnifolia)

Abstract

We studied the persistence of conditioned taste aversions in sheep and whether or not sheep averted to one shrub species would avoid another shrub species. Three-month-old lambs were averted to the shrub Cercocarpus montanus by pairing its ingestion with lithium chloride (LiCl), a nonlethal gastrointestinal poison. When lambs were yearlings, they were offered C. montanus plants growing in 8-liter pots. During the persistence trial, averted sheep took fewer (P less than .05) bites of C. montanus than controls did (19 vs 64 bites/sheep, respectively). Following the persistence trial, sheep that had been previously averted to C. montanus and consumed C. montanus received LiCl. Complete aversion to C. montanus was re-established in previously averted sheep with a single dose of LiCl. When sheep previously averted to C. montanus were offered potted Amelanchier alnifolia shrubs, averted sheep consumed 21 bites of A. alnifolia but controls consumed 58 bites (P less than .05). This result suggests that previously averted sheep were either more food neophobic than controls or generalized their aversion from C. montanus to A. alnifolia. As with C. montanus, a single dose of LiCl completely averted sheep to A. alnifolia. When sheep grazed a pasture containing C. montanus and A. alnifolia averted sheep took fewer (P less than .05) bites of the two shrubs than controls did (.2% vs 18%). Sheep showed no signs of extinguishing the aversion to either shrub during the grazing season (May-Sept.). Aversive conditioning may be useful to manipulate diet selection of free-ranging livestock.