Comportamento da Mosca-dos-chifres, Haematobia irritans, (Diptera - Muscidae) frente aos compostos orgânicos voláteis de diferentes raças bovinas

Abstract

The aim of this work was to study the effect of Volatile Organic Compounds (VOCs) released by cattle of different breeds on the behavior of the horn fly (Haematobia irritans). This ectoparasite is of great economic importance because it causes damage to various livestock worldwide. The study began with the implementation of a breeding place for horn flies in the laboratory at the Federal University of Alagoas in order to perform advanced studies with this parasite, as well as to follow the development of the egg to adult. Three breedings methods were used in order to obtain the greater emergency index of H. irritans fly in laboratory. Afterwards, odors released by cattle breeds Gyr, Holstein, Brown Swiss, Nellore and Gyr (both sexes) were taken followed by the extraction of the material collected with the aid of bidestiled hexane and analysis by Gas Chromatography (GC), Gas Chromatography coupled to Mass Spectrometry (GC/MS) in all breeds; Eletroantenography Gas Chromatography (GC/EAG) performed with the chromatogram with the highest number of peaks and behavioral bioassays. The behavioral bioassays with the horn fly were performed with extracts from animal and synthetic standards identified in GC/EAD, using an olfactometer type Y. In addition, we investigated whether there are differences on VOCs released from the different genetic groups. With regard to the breeding place, in the first creation, horn flies after emergence were counted and the result was 18.61% of emergency. In the second creation, the percentage of emerged flies was 55.56% and in the third was 78.22%, considered, thus, the most appropriate method for rearing H. irritans in laboratory, when the development was within a cooling chamber. Analysis of the GC chromatograms of the Brown Swiss breed showed that the collection of VOCs in animals was efficient since most of the compounds was shown to be present in all samples. The qualitative GC analysis of all races had shown that there was not a large variation with respect to VOCs. The analysis of GC/MS confirmed the difference on compounds between the races, and nine of them were common in all races. Among them, camphene, 2-ethylhexanal, 2-heptenal, 1-octen-3-one, 1-octen-3-ol, octan-3-one, octanal, 2,2,8-trimethyldecane and 2-phenylethyl butyrate. All VOCs obtained in the analyses mentioned above were identified by their Kovats indices indexes (KI). The results of the extracts’ aeration bioassays have shown that insects are attracted by volatiles from both sexes of the European breeds and mixed Girolando. In the bioassays performed with synthetic standards, only butyl acetate showed significant responses at concentrations of 10-7, 10-6 and 10-5 mg/mL. VOCs obtained by GC/MS were similar between breeds and mixed European and otherwise distinct from the Indian races.