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Towards a new phenotype for tick resistance in beef and dairy cattle : a review
Burrow, Heather M.; Mans, Ben J. (Barend Johannes); Cardoso, Fernando F.; Birkett, Michael A.; Kotze, Andrew C.; Hayes, Ben J.; Mapholi, Ntanganedzeni; Dzama, Kennedy; Marufu, Munyaradzi Christopher; Githaka, Naftaly W.; Djikeng, Appolinaire
About 80% of the world’s cattle are affected by ticks and tick-borne diseases, both of which cause significant
production losses. Cattle host resistance to ticks is the most important factor affecting the economics of tick control, but it is
largely neglected in tick-control programs due to technical difficulties and costs associated with identifying individualanimal
variation in resistance. The present paper reviews the scientific literature to identify factors affecting resistance of
cattle to ticks and the biological mechanisms of host tick resistance, to develop alternative phenotype(s) for tick resistance. If
new cost-effective phenotype(s) can be developed and validated, then tick resistance of cattle could be genetically improved
using genomic selection, and incorporated into breeding objectives to simultaneously improve cattle productive attributes
and tick resistance. The phenotype(s) could also be used to improve tick control by using cattle management.Onthe basis of
the present review, it is recommended that three possible phenotypes (haemolytic analysis; measures of skin
hypersensitivity reactions; simplified artificial tick infestations) be further developed to determine their practical
feasibility for consistently, cost-effectively and reliably measuring cattle tick resistance in thousands of individual
animals in commercial and smallholder farmer herds in tropical and subtropical areas globally. During evaluation of
these potential new phenotypes, additional measurements should be included to determine the possibility of developing a
volatile-based resistance phenotype, to simultaneously improve cattle resistance to both ticks and biting flies. Because the
current measurements of volatile chemistry do not satisfy the requirements of a simple, cost-effective phenotype for use in
commercial cattle herds, consideration should also be given to inclusion of potentially simpler measures to enable indirect
genetic selection for volatile-based resistance to ticks.