Studies on the ability of two isolates of Bacillus thuringiensis, an isolate of Clonostachys rosea f. rosea and a diatomaceous earth product to control gastrointestinal nematodes of sheep
2013
Ahmed, M.A. | Laing, M.D. | Nsahlai, I.V.
Nematode parasites have developed resistance to anthelmintics. Biological control of gastrointestinal nematodes (GIN) in sheep is a promising non-chemical control method. Two experiments were done using Merino sheep. In each experiment, gender, initial egg count per gram (EPG) and initial body weight (BW) aided in placing animals into four groups, each of which was randomly fed with one of four treatments. Experiment 1 evaluated anthelmintic effects of Bacillus thuringiensis Berliner (Bt), Clonostachys rosea f. rosea Schroers (C. rosea) and diatomaceous earth (DE) in sheep. Bacillus thuringiensis and C. rosea were fed to sheep at a rate of 1 g kg⁻¹ BW, and DE was fed at 2% of sheep diet. Relative to the control, treatments had no effect (P>0.05) on EPG, but reduced (P<0.001) larvae per gram (LPG) in faecal culture. Efficacy varied with time (P<0.001). On Day 7, Bt, C. rosea and DE had efficacies of 76, 87 and 61%, respectively. In experiment 2, efficacy of feeding 1 g kg⁻¹ BW of C. rosea chlamydospores to sheep every day, every second day and every third day was tested. Daily feeding of fungal chlamydospores had no effect on EPG (P>0.05), but reduced (P<0.001) LPG (12±1.67) more than every second day (39±0.77) or third day (58±1.77). On Day 12, feeding daily, every second day and every third day had efficacies of 90, 63 and 49%, respectively. These studies suggest that each of Bt, C. rosea isolates and DE products has a potential to affect nematode larvae, and daily use of C. rosea had the highest effect as a biological control of nematodes in this study.
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