Now that the complete DNA sequence of 1147 bulls is known to scientists, the hope is that this data can be used to faster determine which bulls are most suitable for breeding. The aim is to breed cows with qualities such as higher milk production or lower greenhouse gas emissions.
The initiative was originally named the 1000 bull genome project, but it has expanded beyond the original target over time. Set up by geneticists from Wageningen, Australia and France, the consortium now counts twenty research groups from around the globe and has determined the DNA sequence of 1147 bulls.
Roel Veerkamp, study director for the Wageningen part of the research, expects the data to provide reliable answers in the future as to whether a bull is suitable for breeding or not. “We used to have to wait at least seven years before we could answer this question,” he states. Since bulls give no milk, it was possible to see whether they had an appropriate set of genes only by observing their daughters – and a bull only has enough daughters to judge his qualities after seven years. But there are already tests that can give an idea of the suitability of a bull based on genetic information. “We wish to increase the reliability of this prediction by using the whole genome,” Veerkamp explains.
Effects of genetic differences
The analysis has shown that the DNA of bulls of different breeds differs in 35 million places. Veerkamp is now joining forces with other scientists to look into the biological effects of these millions of differences. Some of them have clear consequences. For instance, the consortium found two genetic defects in one place in the DNA which had directly visible effects: one results in curly hair, while the other interferes with embryonic development. But most properties, including milk yield, are determined by simultaneous variations in hundreds of genes. This is the real challenge for Veerkamp’s research.
Predicting complex traits for breeding
He is now looking for ways to predict these complex traits based on the millions of variations in the DNA of the animal. “The consortium has chosen a well-researched feature: height. We will look at the DNA variations that are important for this characteristic in different populations and find out which are the best predictors of whether a bull is suitable for breeding. Once we understand better how things work for this model characteristic, we should be able to make the transition to features that are more important for breeding. Then we will be able to say whether a bull is good breeding stock or not soon after he is born.”