A comparative study in ectoparasite tolerance between Purebred Brahman (Bos indicus Linnaeus), sussex (Bos taurus Linnaeus) and brahman x sussex crossbred cattle in the Free State, South Africa
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Crossbreeding Bos indicus with Bos taurus cattle was explored as a measure to manage ectoparasite infestation specifically comparing tick, mite, fly and lice resistance between Brahman, Sussex and Brahman x Sussex crossbreds. The study area was located in the central Free State on different farms, not more than 15km apart, where cattle breeds were followed and ectoparasites collected on a monthly basis from March 2014 to March 2015. The aim of the study was to determine if Brahman cattle have a natural ectoparasite resistance and if this resistance can be linked to certain breed characteristics when compared to other cattle breeds such as Sussex. A second aim was to establish if the resistance qualities identified are preserved in the cross bred generations. Ectoparasites were collected from both the on-host environment by inspecting 20 cattle from each breed every month as well as the off-host environment through tick drags, fluorescent light traps and sticky fly traps. Ectoparasite abundance regarding both the on-host and off-host environment were also compared to mean monthly temperature and rainfall numbers A total of five Ixodidae species were collected from the animals over the study period including Hyalomma rufipes (3797), R. evertsi evertsi (596), H. truncatum (393), R. decoloratus (29) and R. appendiculatus (30). All of the tick species except for H. truncatum showed a higher affinity for the Sussex breed. The Sussex cattle groups also had the most tick infested individuals over the entire test period. Attachment areas for ticks showed Sussex cattle to have nine areas of tick attachment with Red Brahman two, Grey Brahman three and the crossbred cattle with four attachment areas, corresponding more to the Brahman breeds than the Sussex breed. A greater overview was gained of Diptera diversity and abundance as well as the presence of veterinary important Diptera ectoparasites in the Kroonstad region. Rainfall however, seemed to be a factor influencing host preference, for during December 2015, with higher rainfall numbers and a significant higher Diptera species presence, no significant differences of Diptera abundance between any of the breeds were observed. If this is compared to December 2014, when a dry spell occurred, unfavourable conditions caused the presence of lower numbers of Diptera species, and a preference for the Sussex breed was observed. No association was found between on-host and off-host ectoparasite abundance for all ectoparasite species collected, but this needs to be investigated more intensively in future. Seasonal factors like rainfall and temperature had an influence on ectoparasite abundance in the on-host and off-host environment with higher numbers found during the warmer months with higher rainfall. From the results gained it is evident that certain breed characteristics can have an influence on ectoparasite load. Comparison of phenotipic characteristics showed Sussex cattle to have higher ectoparasite loads which correlated to longer, denser, coarser, and darker coats and higher body temperatures. The Grey- and Red Brahman groups had the lowest parasite loads accompanied by shorter and smoother coats and lower body temperatures. Tail length did not play a role in regulating ectoparasite loads. Although Sussex cattle were statistically significantly heavier than the Brahman breeds, they still had the most ticks per kg body weight compared to the Brahman and cross breeds. However, the Brahman x Sussex crossbreed, had a mean weight only 22.9kg lower than those of the Sussex group and 115kg higher than the Brahman breeds with a significantly lower ectoparasite load. This indicated that crossbreeding could be integrated into herd management plans as an effective measure in controlling ectoparasite loads on cattle in both intensive and extensive production systems.