Rearing conditions for lambs may increase tansy ragwort grazing

Grazing by sheep is an accepted method of controlling tansy ragwort (Seneci o jacobaea L.), but some flock members seldom eat it. Our objectives were t o determine if pre-weaning exposure to tansy ragwort increases later consum ption of the plant by lambs, and if confinement with ragwort-eating ewes af ter weaning facilitates ragwort eating. The sampling periods were Weeks 1, 3, and 12 following weaning. During each period grazing behavior was observ ed for 1-hour each day and the 24-hour reduction in ragwort volume measured on each of 4 or 5 consecutive days. Lambs exposed to ragwort before weanin g removed more ragwort than ragwort-naive lambs during the first 2 sampling periods (P < 0.05). Lambs that grazed with ewes for 11 weeks following wea ning ate ragwort more frequently during direct observation, than lambs with out ewes during Weeks 3 and 12 (P < 0.05). The ragwort-eating of all lamb g roups increased markedly between Weeks 1 and 12 (P < 0.05). This may indica te an increased ability of lambs to consume ragwort with increasing age or an acclimation period during which most lambs come to accept ragwort, Behav ioral interventions aimed at increasing the consumption of weeds by lambs m ay need to take into account age-related differences in toxin tolerances. E xposing lambs to ragwort before weaning and grazing newly-weaned lambs with older ragwort-eating sheep after weaning may increase later ragwort-eating by lambs.