The findings, published in Nature Genetics, emerged from a collaborative effort to sequence the genomes of 172 indigenous cattle.
The scientist wanted to learn how, after spending thousands of years confined to a shifting patchwork of sub-regions in Africa, cattle rapidly evolved during the last millennia with traits that allowed them to thrive across the continent.
“We believe these insights can be used to breed a new generation of African cattle that have some of the qualities of European and American livestock, which produce more milk and meat per animal, but with the rich mosaic of traits that make African cattle more resilient and sustainable,” said Olivier Hanotte, principal scientist at ILRI, professor of genetics at the University of Nottingham and programme leader at CTLGH, who led the work at ILRI.
Hanotte and his colleagues were engaged in a kind of “genomic time travel” that, for the first time, allowed scientists to retrace the genetic journey that made African cattle so adaptable. They discovered what co-author Steve Kemp, head of ILRI’s LiveGene programme and deputy director of CTLGH described as an “evolutionary jolt” that occurred between 750 and 1050 years ago: the arrival of Asian cattle breeds in East Africa with genetic traits that would make cattle production possible in diverse and demanding African environments.
The genome-sequencing work has shown that indigenous pastoralist herders have begun breeding Asian cattle, known as Zebu, with local cattle breeds known as Taurine. In particular, Zebu offered traits that would allow livestock to survive in hot, dry climates typical of the Horn of Africa. But by crossing the two, the new animals that emerged also retained the ability of the Taurines to cope with humid climates where vector-borne diseases such as trypanosomiasis are common.
“Livestock, especially cattle, can be controversial, but without them, millions of people in Africa would have been forced to hunt wildlife for protein,” said co-author Ally Okeyo Mwai, a principal scientist at ILRI who leads its African Dairy Genetic Gains programme. “That would have been devastating for the African environment and its incredible diversity of wildlife.”
It is now important to use the full range of natural genetic resources that have made African cattle so resilient to meet Africa’s growing demand for milk and meat while minimising the negative impact of increased livestock production. For many households in Africa, and especially the poorest, livestock in general and cattle, in particular, continue to be the most valuable asset of the family.
They provide a critical source of protein and micronutrients alongside income to pay for things like school fees. They also provide manure for crops, and some African cattle breeds can survive under conditions that can not support food crops, offering farmers a potential climate change adaptation strategy.
“You can see from studying the genomes of indigenous cattle that breeding for environmental adaptation has been the key to successful livestock production in Africa,” said Kemp. “And that has to be the factored in our future efforts to develop more productive, more sustainable animals. If the goal is pure productivity, you’re doomed to fail.”