Conditioned aversion to minimize Ferula communis intake by orphaned lambs

The circum-Mediterranean perennial Ferula communis L. (giant fennel) has an ticoagulant constituents. Mortality from poisoning can affect 5% of the she ep grazed in infested areas and most casualties are ewe-lambs at the onset of the grazing season. In intensive sheep production systems, ewe-lambs are "orphaned", artificially reared, and have no opportunity to acquire safe d ietary habits by imitating their mothers. The aim of the present study was to evaluate the intake of F. communis in such lambs and to assess the poten tial of using conditioned aversion as a managerial tool to decrease the fre quency of F. communis poisoning. Six lambs weighing approximately 28 kg wer e averted to F. communis using 2 administrations of 4g LiCl in aqueous solu tion, given immediately after a meal of F, communis: 6 similar lambs served as unaverted controls. The intake of F. communis and the persistence of av ersion were assessed over 7 observation days using a simulation of an infes ted field where freshly cut bunches of F. communis were tied to stakes at 1 0-m intervals in ryegrass (Lolium multiflorum Lam.) paddocks at the late ve getative stage. Averted lambs grazed separately from unaverted counterparts . Time spent by lambs foraging on F, communis was in the range of 0-0.015 m in/hour (not significantly different from nil) in averted, and 0.15-0.24 mi n/hour in unaverted lambs, respectively (P = 0.002). Consequently, the rate of disappearance of F. communis was greater when grazing;vas by unaverted than averted lambs (0.29 and 0.15 g/min, P = 0.01). The aversion persisted for 25 days after the LiCl treatment, at which time observations were disco ntinued. Assuming that the amount of F. communis that disappeared is close to actual intake by lambs, intake by unaverted lambs was high enough to end anger the lambs, whereas averted lambs consumed safe amounts of the poisono us plant. It is concluded that conditioned aversion has the potential to al leviate the problem of F. communis poisoning in orphaned ewe-lambs.