Researchers from the Centre for Tropical Livestock Genetics and Health (CTLGH) have developed a technique to successfully reproduce a naturally occurring gene mutation that can improve the thermotolerance of cattle living in hot countries.
This work will particularly benefit low-and middle income countries (LMICs), as they are typically situated in tropical and sub-tropical regions of the world where increased environmental temperatures associated with global warming are predicted to exacerbate already difficult farming conditions.
This technology could be used to establish a population of native breeding animals in tropical countries with the SLICK trait that are better adapted to elevated temperatures due to climate change and remain culturally accepted by the local farmers.
Because this trait is associated directly with a heritable genetic change these cattle will be able the pass it on to their future offspring through natural breeding.
Note the difference in the hair coverage of these two cows. The cow on the left has naturally occurring gene mutation that leads to the display of the SLICK trait, the cow on the right does not. Photo credit: Littlejohn et al, Nat Commun 5, 5861 (2014). https://doi.org/10.1038/ncomms6861
Heat stress and the SLICK gene
Productive cattle eat grass, digest it and produce meat and/or milk. As part of this process they generate heat, and in temperate environments are able to lose excess heat to the environment. Heat stress occurs when animals are unable to maintain a core body temperature within their normal physiological range, and has negative impacts on the animal’s welfare, productivity and immunity and is a particular concern in LMICs
Certain breeds of European (taurine) cattle can display a trait called SLICK, characterised by reduced hair coverage and reduced susceptibility to heat stress. The SLICK trait is caused by one of several natural mutations in the prolactin receptor gene.
Natural crossbreeding with cattle with the SLICK trait could be used to introduce this thermotolerance trait into indigenous cattle in LMICs, but admixture between European and native breeds would invariably result in dilution or loss of other desirable phenotypes and as such may not be accepted by local communities.
Genome editing has provided an alternative solution to as it allows researchers to introduce the single nucleotide changes underlying SLICK directly into native breeds.
Introducing the SLICK trait
CTLGH researchers based at the Roslin Institute have developed an electroporation strategy that successfully modifies the prolactin receptor gene in newly fertilised eggs from non-SLICK cattle to match that of a SLICK animal. These modified embryos were then transferred into surrogate hosts to produce healthy calves showing the SLICK trait.
The CTLGH team at the Roslin Institute have shared their methodologies with CTLGH colleagues based at the International Livestock Research Institute (ILRI) in Nairobi, who will look to mirror the approach in native Kenyan cattle breeds.
As global warning constitutes a real and considerable global concern, heat stress is likely to become more relevant in other species globally. As part of an EU consortium the research team at the Roslin Institute have recently secured a Horizon 2020 grant to produce and assess sheep with similar modifications to the prolactin receptor gene.
Dr Simon Lillico, who led the research at CTLGH and the Roslin Institute commented:
“The world’s climate is changing and temperatures are set to increase. Establishing livestock with the appropriate genetics to increase their resilience to the challenges of climate change, particularly in tropical countries, will not only improve the animals overall health and welfare, but will also maximise their productivity and therefore reduce their overall carbon footprint.”
Providing solutions for farmers in the tropics
For the millions of smallholder farmers living in LMICs, the livestock they keep provides both income and nutrition for their family and serves as a hedge against the impacts of the climate crisis on their farms and a pathway out of poverty.
Africa’s population is increasing at the fastest rate across the globe. In a continent where malnutrition is commonplace, improving the productivity and health of the native livestock is vital. As many biological traits, including those involved in productivity, disease resistance and environmental resilience, have a genetic component, improving the genetics of the native African breeds could help provide a lifeline for the 250 million people across the continent who currently go to bed hungry.
**CTLGH receives funding from the Bill & Melinda Gates Foundation (BMGF), the UK Foreign Commonwealth and Development Office (FCDO), the UK Biotechnology and Biological Science Research Council (BBSRC) and Jersey Overseas Aid (JOA) **
