Genetic Basis of Disease Resistance and Heat Tolerance analysed in Gir

Dr. A. Samad

Gir cattle of the Zebu class have become popular worldwide for being hardy, resistant to infectious and parasitic diseases (external as well as internal). With overt changes in climate and wide-spread global warming animal scientists are concerned that milk production may fall drastically as European and American breeds are not tolerant to warm and humid climates, whereas heat tolerant breeds are low milk producers. Amongst Zebu, Gir breed cattle have received wide attention as it is a comparatively high milk producer. One way to address this challenge is to develop a synthetic breed having good production traits of Bos taurus (humpless) with Zebu such that the crossbreds carry good traits of Zebu breeds too. For this, scientists have been exploring with keen interest genetic basis of heat tolerance and disease resistance.

University of Alberta in collaboration with ‘Genus Inc’, a breeding services company from USA have published an interesting article on whole genome sequencing of three Gir bulls independently whereas pooled sample was obtained from 11 Gir bulls.

The paper was authored by X. Liao, F. Peng, G. Plastow, G. Stothard (All from University of Alberta) and S. Forni and D. McLarne (both from Genus plc, WI, USA), 2016.

Interesting findings were:

• A total of 9990733 SNPs and 604308 insertions and deletions were discovered out of these 62.3% and 83.62% respectively were previously unknown.
• 79 putative section sweeps using sequence data of pooled samples were also discovered.
• One such sweep has been found to harbour several genes of cathelicidin family. These genes are associated with resistance to pathogens and parasites.
• Another region was found to harbour genes associated with mitogen-activated protein kinases. These genes are known to be responsible for immunity.
• Another region was found to harbour genes associated with heat-shock proteins that confer heat tolerance.

These findings would act as foundation for further work to understand if good genes can be transmitted by employing genetic manipulation techniques. This article reiterates that heat and disease tolerance has a genomic basis and that it should be possible to develop synthetic breed with crossing of Zebu and Taurus breed of cattle if scientific methods are followed.