Pierce Rafter, ICBF, presented a board in the Breeding and Reproduction Village at the recent Moorepark Open Day. The board highlighted the importance of incorporating DNA in decision making.
Over the last 20 years, the technological capacity to decode DNA, a process which is known as genotyping, has increased massively. Incorporating DNA information into breeding decisions has increased the efficiency of cattle breeding compared to traditional breeding methods which relied only on ancestry records to evaluate the genetic merit of animals. Traditional evaluations predict cattle performance based on the performance of their known family members. DNA information can be used to directly analyse the unique DNA profile of cattle and generate a bespoke prediction of genetic merit. This is a more nuanced and accurate approach because it captures both the family-based performance and the unique attributes of the animal itself.
The increased accuracy of genomic evaluations has multiple benefits. Firstly, selection decisions are more accurate which increases the rate of genetic improvement, and therefore, profit for the farmer. Secondly, genomic evaluations require less data (e.g., fewer daughter records) compared to traditional evaluations to get the same level of accuracy. Therefore, selection decisions can be made sooner and more cheaply which in turn increases the rate of genetic improvement by shortening generation intervals.
The benefits of genotyping are not just restricted to more profitable breeding decisions. Genotyping has a host of other benefits such as:
- correcting misassigned parentage, misassigned breed, and misassigned sex for 17.4%, 3.2%, and 1.6% of genotyped calves, respectively.
- Evaluating the commercial beef value (CBV) of calves. This is a DNA derived metric which is used to help calf-to-beef farmers predict which calves are the most valuable for a calf-to-beef farming enterprise.
- DNA information is also essential for reporting on genetic variants of myostatin, polled Celtic, and other important genes.
- Access to tools such as GenoCells which can be used to efficiently identify cows with mastitis when the entire milking herd is genotyped.
Another benefit of genotyping, particularly of calves, is the identification of chromosomal abnormalities. In cattle, DNA is not one continuous chain instead it is split into discrete blocks known as chromosomes. Each chromosome exists as a pair; one chromosome is inherited from the father and the other chromosome is inherited from the mother. Sometimes in reproduction one of the chromosomes in a pair can be lost or doubled. If this loss or doubling of a chromosome happens with a sex chromosome (the chromosomes which determine if a calf is male or female) the animal can appear normal, but be infertile. An estimated 0.04% – 0.08% of calves born annually will have an abnormal number of sex chromosomes.
In summary, DNA genotyping is an extremely valuable technology. Genotyping increases the accuracy of predicted breeding values, reduces the burden of data collection, can correct recording errors, report genetic variants in major genes, and efficiently identify calves with chromosomal abnormalities that will never reproduce.