Glimpses of Research on Indian Cattle

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Extract from Genome-wide Analysis of the Heat Stress Response in Zebu (Sahiwal) Cattle

by Kusum Mehla, Ankit Magotra et al.  National Dairy Research Institute Karnal, Haryana

Indian breeds of cattle are known to be tolerant to heat and humidity—a characteristic that is growing all the more relevant in view of the threat of global warming. There have been a number of attempts to understand the basis of this tolerance. Earlier it was held that this was merely due to acclimatisation. With recent advances in the field of genomics, however, it has been suggested that these traits may have a genetic basis. This topic is of great importance even from the point of view of Indian farmers, since the tropical climate has been indicted to be the cause of low production and infertility. Understanding the genetic basis of both characteristics could help scientists work towards synthesizing a good breed of cattle.

Scientists from the National Dairy Research Institute have conducted genomic studies in which they sought to study the mRNA expression in Sahiwal cows that were exposed to severe heat, and compare it to the same in heifers that were exposed to normal temperature and humidity. They exposed the heifers to 42 degree heat for 4 hours and then took a blood sample from which they extracted RNA. The same cows were then allowed to rest at room temperature and their blood was collected again for RNA analysis. The technique they used is called microarray. They found gene expression changes in activation of heat shock transcription factor 1 (HSF1), increased expression of heat shock proteins (HSP) and decreased expression and synthesis of other proteins, immune system activation via extracellular secretion of HSP. Further analysis using the cDNA microarray technique found 140 transcripts to be up-regulated and 77 down-regulated in the cattle blood after heat treatment (P < 0.05). The research gave a fair idea that body responses to heat have a genomic basis. The next challenge is to go beyond the transcript and identify the exact gene or genes responsible.