Effects of feeding willow (Salix spp.) upon death of established parasites and parasite fecundity

Two indoor feeding experiments with young sheep were conducted to compare effects of feeding condensed tannin (CT) containing willow ( Salix spp.) or chaffed lucerne hay ( Medicago sativa ) upon death of established parasites and parasite fecundity. In Experiment 1, 24 parasite-free weaned male lambs were individually penned, fed chaffed lucerne hay ad libitum for 5 weeks and then fed either lucerne ( n = 12) or willow ( n = 12) diets for a further 5 weeks. Twelve days prior to willow feeding, all lambs were infected with a mixed population of 22,300 gastrointestinal nematodes comprising predominantly Teladorsagia spp. (0.93), with the remainder being Trichostrongylus , Cooperia and Haemonchus species. Voluntary feed intake, apparent digestibility, blood composition, faecal nematode egg counts, production of eggs and hatched larvae, female worm fecundity and worm burden at slaughter were measured. In Experiment 2, Teladorsagia eggs were added to the faeces of parasite-free sheep fed either lucerne or willow ( n = 9) to measure proportional recovery. Recovery of added Teladorsagia eggs was 0.85 in lucerne-fed lambs and 0.53 willow-fed lambs (P versus 0.83 of eggs added). In Experiment 1, total CT concentration in willow was 27 g/kg DM, with only traces in lucerne, while organic matter digestibility was 0.648 versus 0.599 (P Haemonchus contortus (P Teladorsagia circumcinta (P Haemonchus and Teladorsagia spp. (P i.e. , eggs produced/worm/day) for H. contortus (P in utero as a measure of fecundity in both T. circumcincta and Trichostrongylus spp. (P 3 larvae for both H. contortus and T. circumcincta (P Feeding willow to parasitised young sheep reduced nematode worm burdens and female worm fecundity, with abomasal dwelling species being most affected and conventional methods of measuring FEC underestimated nematode eggs in the faeces of willow-fed sheep.