Effects of sulla condensed tannins on the viability of three
sheep gastrointestinal nematodes
A.L. Molan, R. Alexander, I.M. Brookes and W.C. McNabb
Nutrition and Behaviour Group, AgResearch, Grassland Research
Centre, Private Bag 11008, Palmerston North, New Zealand
Proceedings of the New Zealand Society of Animal Production.
2000 60: 21-25
The effect an extract of sulla (Hedysarum coronarium) containing
condensed tannins (CT) had on the viability of the infective third-stage
larvae (L3) of three gastrointestinal nematodes (Haemonchus contortus,
Ostertagia circumcincta and Trichostrongylus colubriformis) was tested
by the larval migration inhibition (LMI) assay in vitro. The LMI assay
measures the ability of test material to immobilize larvae and prevent
their migration through 20 mm nylon mesh sieves. The extract from sulla
was added to rumen (RF) and abomasal fluid (AF), collected from sheep
fed lucerne (Medicago sativa) chaff, to provide concentrations of CT
similar to those observed in the rumen and abomasal digesta of sheep fed
CT-containing forages (50-1000 mg/ml). Incubation of L3 larvae in rumen
and abomasal fluid containing the sulla extract reduced the migration of
larvae compared to those in control incubations (no extract added). This
study showed that the larvae of T. colubriformis were more resistant
(P<0.001) to the inhibitory effects of the sulla extract than were the
larvae of the other nematodes. When the larvae of these nematodes were
incubated in rumen and abomasal fluid containing 1000 mg CT/ml, the LMI
values for O. circumcincta (RF 59%; AF 79%) and H. contortus (RF 72%; AF
81%) were significantly (P<0.001) greater than for T. colubriformis (RF
37%; AF 26%). Addition of 2 mg polyethylene glycol (PEG)/ mg CT to the
incubations partially reduced the effects of the sulla extract on larval
migration, particularly in the rumen fluid, suggesting that CT was
responsible for most but not all of the inhibitory effect of this
extract.
Keywords: NZSAPAB;
sulla; condensed tannins; sheep; gastrointestinal nematodes.
Last Updated 12-07-2000
