Significance of moisture content of dung pats for colonisation and degradation of cattle dung.

The moisture content of freshly voided cattle faeces is important with regard to colonisation by fauna and the rate of degradation of dung pats. This paper reports five trials designed to clarify the influence of small changes in moisture content of dung pats on dung breeding Coleoptera, Diptera, nematodes and earthworms and on degradation of the pats. Surface area, wet weight and organic substance content were used as parameters for measurement of degradation. Special attention was given to a trial which compared naturally voided pats with pats formed artificially from faeces of the same animals. Results indicate that small differences in moisture content of 1-2%, which may not be distinguishable by visual inspection, may have an impact on the development of Diptera, Coleoptera and earthworms and on dung degradation.

Colonisation and degradation of dung pats after subcutaneous treatment of cattle with ivermectin or levamisole.

The fauna and degradation of dung pats from cattle treated with ivermectin or levamisole were examined in a field study conducted in southern Germany. Four groups of seven cattle each grazed on four paddocks. The cattle were treated subcutaneously with ivermectin (0.2 mg/kg) or levamisole (5 mg/kg) 3, 8 and 13 weeks after turnout. A total of 300 pats voided naturally before the first and third treatment and 3, 7, 14 and 28 days after treatment were evaluated. Half of them were used as sampling pats, in which adult and immature Coleoptera, larvae of Diptera and soil and dung nematodes were counted. Earthworms were weighed in samples taken on 8 occasions within 63 days after pat deposition. Dung degradation was investigated using 150 observation pats by measuring surface area, weight and organic matter content on six occasions within 63 days from deposition. A photographic record was also maintained. There was no difference between treatment groups as to the range of Coleoptera, nematodes and earthworms collected from the pats. No quantitative differences between groups were seen regarding the total number of adult and immature dung beetles, soil nematodes and earthworms isolated within 63 days after deposition. Populations of Diptera larvae in pats voided up to 28 days after treatment were reduced for the ivermectin treated group relative to the levamisole group. There were reductions in numbers of dung specific nematodes in pats from both groups and some species were reduced in pats deposited 3, 7, and to a lesser extent, 14 days after treatment for the ivermectin group compared with pats from the levamisole group. These effects on dung fauna had no impact on dung degradation. The results of serial measurement of pat area, photographic evaluation, and determination of remaining dung weight and organic matter showed no difference between treatment group.

The degradation of dung produced by cattle treated with an ivermectin slow-release bolus.

Eight female calves of the Deutsches Fleckvieh breed, weighing 161-207 kg, were each treated at turnout on 16 May 1989 with one ivermectin sustained-release intraruminal bolus designed to release ivermectin at 12 mg day-1 for approximately 120 days. Eight animals remained as untreated controls. A third group of eight unmedicated tracer calves was not considered as part of this evaluation. All 24 animals grazed together on a single pasture throughout the study. On Days 21/22, 70 and 119, 15 faecal pats were selected from each treatment group and ranked according to surface area; within each group of three consecutively ranked pairs of pats, two pairs were randomly allocated as observation pats and the third as a sampling pat. The surface area of observation pats was measured, photographs taken, and dry matter, crude ash and organic matter determined at various intervals following deposition. A 1/4 sample collected from sampling pats 3, 7, 14 and 28 days after deposition was weighed and examined for Coleoptera (adults and larvae), Diptera larvae and nematodes. No differences between groups were seen in respect of organic matter content, numbers or frequency of adult Coleoptera species and soil nematodes. A decrease in numbers of Coleoptera larvae, Diptera larvae and dung-specific nematodes was observed in pats from ivermectin-treated cattle. Based on the evaluation of the surface area, a delay in the degradation rate of pats from treated compared with those from untreated animals was seen; however, the difference was statistically not significant (P > 0.05).

Efficacy of abamectin against ectoparasites of cattle.

Four trials, using 48 European breed cattle, were conducted to evaluate the efficacy of abamectin against the louse species Linognathus vituli, Haematopinus eurysternus and Damalinia bovis and against the mange mites Sarcoptes scabiei var bovis and Psoroptes ovis. Animals were allocated by restricted randomisation based on parasite counts to treatment with abamectin at a dose of 200 micrograms/kg given subcutaneously or to an untreated control group. Ectoparasites were counted before treatment and at weekly intervals thereafter for eight weeks. L. vituli, H eurysternus and S scabiei var bovis were eliminated (P < 0.05) by day 7 after abamectin treatment. An efficacy of more than 99 per cent was recorded against P ovis mange mites. The biting louse D bovis was not controlled. Abamectin treatment increased the weight gain of cattle infested with ectoparasites.

Efficacy of abamectin against nematodes in cattle.

Eight controlled trials were conducted, using 96 cattle of European breeds, to evaluate the efficacy of abamectin against natural and artificially acquired infections of adult and fourth-stage larvae of all the economically important gastrointestinal nematodes and lungworms in Germany and the United Kingdom. Half the animals were treated on one occasion with abamectin at a dose of 200 micrograms/kg bodyweight given subcutaneously while the other half remained untreated. Worms were counted 14 or 21 days after treatment or 28 days after the last infection. The treatment was highly effective (> 99 to 100 per cent) (P < 0.05) at removing immature (L4) stages and adult worms of the following species: Ostertagia ostertagi (inhibited larvae included), Trichostrongylus axei, Haemonchus contortus, Bunostomum phlebotomum, Cooperia species Oesophagostomum radiatum and Dictyocaulus viviparus. Naturally acquired adult C surnabada and Trichuris discolor infections were also significantly (P < 0.05) reduced. For Nematodirus helvetianus the efficacy varied from 89.8 to > 99 per cent (P > 0.1 to < 0.01). Abamectin gave full protection against the gastrointestinal nematodes O ostertagi, H contortus, Cooperia species and O radiatum for at least seven days and against the lungworm D viviparus for at least 14 days after treatment.