Abstract
An experiment was performed during the grazing seasons of 1998, 1999 and 2000 to study the influence of the antiparasitic drug ivermectin and the nematophagous fungus Duddingtonia flagrans on cattle dung disintegration. The faeces originated from groups of animals that were part of a separate grazing experiment where different control strategies for nematode parasite infections were investigated. Each group consisted of 10 first-season grazing cattle that were either untreated, treated with the ivermectin sustained-release bolus, or fed chlamydospores of D. flagrans. Faeces were collected monthly on 4 occasions and out of pooled faeces from each group, 4 artificial 1 kg dung pats were prepared and deposited on nylon mesh on an enclosed pasture and protected from birds. The position of the new set of pats was repeated throughout the 3 years of the study. Each year, the dung pats were weighed 4, 6, 8 and 10 weeks after deposition and immediately afterwards replaced to their initial positions.Results showed that there was no difference in faecal pat disintegration between groups. However, the time-lag between deposition and complete disintegration of the faeces varied significantly between deposition occasions. Dung pats disappeared within 2 weeks (visual observation) when subjected to heavy rainfall early after deposition, whereas an extended dry period coincided with faeces still remaining 12 months after deposition.
Highlights
There is probably no other habitat where so many organisms in such large numbers act simultaneously in the processes of biological decomposition, than in the dung of grazing livestock (Lodha 1974)
No faeces remained in early May 2001. Results from this 3-year experiment failed to show any significant differences in the disintegration rate of dung pats derived from cattle that were either treated with the ivermectin sustained-release bolus, or fed the nematophagous fungus D. flagrans, compared with untreated animals
This is much higher than the 1.18 mg/kg faeces found by Alvinerie et al (1999) in dung from cattle treated with the Ivomec SR bolus device (MSD AGVET, Paris, France), which is equivalent to the ivermectin bolus used in this trial
Summary
There is probably no other habitat where so many organisms in such large numbers act simultaneously in the processes of biological decomposition, than in the dung of grazing livestock (Lodha 1974). Later in the mid 1990's, when ivermectin administered through a sustained-release device (bolus) was introduced, veterinarians and farmers were provided with a highly effective tool for nematode parasite control of cattle. Barth et al (1993) reported no significant difference in total numbers of soil nematodes in dung pats from cattle treated with the ivermectin bolus when compared with non-treated animals. Recent research has shown that biological control of nematode parasites in livestock with the nematophagous fungus Duddingtonia flagrans may become part of an organically acceptable alternative (for review, see Larsen 2000). Parasite control is obtained by the trapping hyphal structures of this fungus, which have the ability to capture and destroy larval stages of the nematodes before they migrate to herbage and become available to grazing animals (for review, see Larsen 1999)
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