Climate change is a major concern for the agricultural industry, particularly for livestock farmers. Rising temperatures and extreme weather events can have a significant impact on the health and productivity of cattle.
Heat stress can cause reduced milk production, lower conception rates, increased susceptibility to diseases, and even death.
Therefore, finding ways to improve the heat tolerance of cattle is crucial for ensuring food security, animal welfare, and economic sustainability.
How genetics affect heat tolerance in cattle
Gaston Brito Miserocchi/Getty Images
Different breeds of cattle have different levels of heat tolerance, depending on their origin and adaptation.
Breeds that originated in warm climates, such as Brahman, N'Dama, and Tuli, often have adaptive advantages to heat stress, such as lighter coat color, shorter hair length, larger ears, more sweat glands, and higher blood flow to the skin.
These traits help them dissipate heat more efficiently and maintain their body temperature within a comfortable range.
However, these breeds also tend to have lower milk production and quality than breeds that originated in cooler climates, such as Holstein, Jersey, and Brown Swiss.
These breeds have been selected for high milk yield and fat content, but they also have thicker coats, smaller ears, fewer sweat glands, and lower blood flow to the skin.
These traits make them more vulnerable to heat stress and reduce their performance under high temperatures.
Therefore, there is a trade-off between heat tolerance and milk production in cattle breeds. Farmers have to balance these two aspects when choosing which cows to breed and which to put out to pasture.
However, this trade-off may not be fixed, as there is genetic variation within each breed that can affect their response to heat stress.
By identifying and selecting the genes or gene markers that are associated with heat tolerance, farmers may be able to improve the heat resilience of their cattle without compromising their milk production.
Gene editing is a technique that allows scientists to introduce precise changes in the DNA of an organism.
By using gene-editing tools such as CRISPR-Cas9, scientists can target specific genes that are related to heat tolerance and modify them in a desired way.
For example, one of the genes that has been shown to influence heat tolerance in cattle is called slick.
This gene causes a natural mutation that reduces the hair length and density of some cattle breeds, such as Senepol and Carora.
Cows with this mutation have a slick coat that helps them cope with high temperatures better than cows with normal coats. They also have higher milk production and fertility than other tropical breeds.
Scientists have developed a gene-editing technique that can introduce the slick mutation into any breed of cattle.
By applying an electric field to fertilized eggs from non-slick cattle, they can deliver genome editors that can modify the slick gene in the embryos.
The modified embryos can then be transferred into surrogate cows to produce healthy calves with the slick trait.
This technique has several advantages over conventional breeding methods. First, it can speed up the process of introducing the desired trait into a population.
Instead of waiting for several generations of crossbreeding and selection, gene-editing can produce slick calves in one generation.
Second, it can preserve the genetic diversity and identity of the original breed. Instead of diluting or losing other traits that are desirable or adapted to local conditions, gene editing can only change the trait that is related to heat tolerance.
Third, it can avoid ethical and social issues that may arise from introducing foreign breeds or transgenic animals into native populations.
Gene-editing can create animals that are genetically identical to their parents except for the targeted trait.
Gene editing is not only applicable to the slick trait but also to other genes that may affect heat tolerance in cattle.
For instance, scientists are also exploring genes that are involved in sweating, blood flow, metabolism, immunity, and reproduction.
By editing these genes in combination or individually, scientists may be able to create cattle that are more resilient to climate change.
