Creating aversion to giant fennel (Ferula communis) in weaned orphaned lambs

The circum-Mediterranean perennial Ferula communis (giant fennel) contains anticoagulant constituents and is the most widespread toxic plant in Israel . Most casualties are ewe-lambs at the onset of their first grazing season. We studied the feasibility of implementing conditioned food aversion (CFA) to F. communis in 2-month-old orphaned ewe-Iambs recently weaned from an a rtificial milk dispenser. A procedure of CFA against vetch hay was first el aborated, using a single dose of LiCl administered by drug pistol simultane ously with first-time feeding of vetch hay. The persistence of aversions wa s evaluated at days 3, 6, 9 and 16 post-dosing. A dosage of 133-mg LiCl kg( -1) BW was ineffective in creating aversion. Aversions created by doses of 266- and 400-mg LiCl kg(-1) BW persisted 3 and 9 days, respectively. In an experiment aimed at lengthening the persistence of aversion to vetch hay, i t appeared that: (i) persistence of 16 days could be achieved by using a do uble dosing procedure with a 3-day interval between doses; (ii) 400-mg LiCl kg(-1) BW was lethal to 7/10 lambs; and (iii) there may be an interaction between post-weaning learning of solid food ingestion and the CFA procedure . In a third experiment, six lambs, which had been accustomed to F. communi s for 1 week, were averted to F. communis by administrating two doses of 26 6-mg LiCl kg(-1) BW at 3-day intervals at the time of F. communis meals; si x lambs served as unaverted controls and four lambs were averted to vetch h ay. Aversion to F. communis and vetch hay persisted for 31 and 16 days, res pectively, in lambs kept in individual cages. The lambs were then turned ou t to pasture on a F. communis-infested artificially-constructed paddock div ided into two plots differing in standing biomass of Italian ryegrass, Lamb s averted against F. communis consumed 28% less F. communis than unaverted counterparts. The aversion persisted 46 days after first LiCl administratio n. Lambs consumed more F. communis and CFA was more effective when pasture standing biomass was low (1060 kg DM ha(-1)), compared with medium (2070 kg DM ha(-1)). We conclude that: (i) averting young 'orphaned' weaned lambs t o F. communis is feasible; (ii) LiCl may be lethal to young lambs and the p rocedure used to avert them to F. communis may interact with post-weaning g rowth check; and (iii) the effectiveness of aversion is affected by the con dition of the F. communis-infested paddock in which lambs are to be grazed. (C) 1998 Elsevier Science B.V. All rights reserved.