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Livestock farming under tropical and subtropical climate conditions faces several major problems. Of similar importance as the seasonal lack of fodder and pastures and the lack of water are the biological constraints due to insects of medical and veterinary elevance. Insects especially of the order Diptera are causing severe nuisance, transmitting diseases to animals and humans and carry the possibility of transferring zoonotic diseases. During the rainy season the impact on the general well-being of animals and human beings takes on considerable dimensions and limits the local animal production causing significant economic losses. The situation is complicated by a general trend towards increasingly intensified agricultural production systems.
In this study an ecologically sound and economically feasible innovative insect control method has been evaluated under subtropical climate conditions. The project studied the efficacy of insecticide treated nets which were attached around animal enclosures with the intent to protect the livestock against insect attacks. The innovative element was the simultaneous protection of all cattle kraals inside the intervention village whereas all previous studies on this subject had focused on protecting cattle in single animal enclosures, stables or pastures. Two Fulani settlements in south-west Burkina Faso, West Africa, were chosen as the study and the control site; they are located in the district of Bama near the city Bobo-Dioulasso. The semi sedentary Fulani practice the so called agro-pastoralism which means that their activity is focusing on keeping cattle and farm cropping. The study animals were mainly represented by crossbreeds of Zebu cattle and the trypanotolerant Baoulé.
Differences in the abundance of relevant insects before and after the study intervention were determined; therefore different entomological methods were applied. Three models of insect traps (Ngu traps, sticky traps and BioGents© Sentinel traps) were deployed in weekly intervals in the two villages. Video sequences of protected and control animals were recorded to visualize defense movements against insects. The insect infestation on milking equipment was shown by taking digital photos.
To demonstrate the impact of the insecticide treated nets on the productivity ratios, the weight gain of calves was recorded twice a month over the period of the study; additionally the milk yield of lactating cows was monitored in weekly intervals.
Questionnaires about socio-economic aspects and the subjective perception by the villagers concerning the insect problem and the efficiency of the impregnated nets were carried out at the beginning and the end of the study. The persistence of the active substance in the net, the pyrethroid Deltamethrin, was evaluated over 5 months.
Though reductions in problem insects after netting intervention were repeatedly observed, the results from the analysis of trapped insects were not consistent, which could be related to a variety of irregularities and complications including technical failures of the traps and difficulties in communication with the villagers. The video records of defensive movements showed improvements distinct for protected cattle compared to control animals; likewise, the photos of milk equipment show a marked reduction of flies on the intervention sites. These results are a clear indication of the benefits of the fence use though the significance of both visualization methods is limited by a small quantity of data points. The results of the weighing of calves were indicative of a positive influence of the protection though missing statistical significance. The records of milking yields by the study participants appeared to be heterogeneous, which reduced the validity of these results.
The analysis of the questionnaires confirmed the comparability of study and control village, thereby emphasizing the hypothesis of a reduction of insect abundance after protection and showed a high level of acceptance by the livestock keepers. The net material proved sufficiently effective against pyrethroid-sensitive laboratory flies over a period of 5 months. The net material proved to be robust and therefore suitable for the use under tropical field conditions.
Future studies should focus on answering questions concerning a demand-based distribution, the sustainability of insecticide treated nets and the attachment of the net to different substrates (as trees, house walls etc.). The quality management of data acquisition should be improved.