Genomic Testing Can Decrease Genetic Lag19 May 2015
Until now, genomic information has mainly been used to improve the accuracy of genomic breeding values for breeding animals, but recent Danish research shows it can also be used to reduce genetic lag.
The Danish researchers hypothesised that the use of information from genotyped females would open up the possibility of reducing genetic lag in a dairy herd.
Genetic lag occurs when the farmed animals of a particular breed lag behind the breeding herd in terms of genetic merit.
The scientists felt the opportunity to reduce genetic lag occurs especially if genomic tests are used in combination with sexed semen or an increased level of reproductive management.
In this study, sexed semen was used in combination with beef semen to produce high-value crossbred beef calves. Thus, on average there is no surplus of and selection among replacement heifers whether to go into the herd or to be sold.
In this situation, the selection opportunities arise when deciding which cows to inseminate with sexed semen, conventional semen, or beef semen.
They tested the hypothesis of decreased genetic lag by combining the results of two computer simulation models, known as SimHerd and ADAM.
SimHerd estimates the economic effect of different strategies for use of sexed semen and beef semen at three levels of reproductive performance in a dairy herd. Besides simulating the operational return, SimHerd also simulates the parity distribution of the dams of heifer calves.
The ADAM program estimates genetic merit per year in a herd under different strategies for use of sexed semen and genomic tests.
The annual net return per slot was calculated as the sum of operational return and value of genetic lag minus costs of genomic tests divided by the total number of slots.
The results showed that the use of genomic tests for decision making decreased genetic lag by as much as 0.14 genetic standard deviation units of the breeding goal. They also showed that genetic lag decreased even more when genomic tests are used in combination with strategies for increasing and using a reproductive surplus.
Of course, genetic test cost is a significant factor in the total impact on profitability.
The scientists also observed that genomic tests are used most efficiently to decrease genetic lag when the genomic information is used more than once in the lifetime of an animal and when as many selection decisions as possible are based on genomic information.
However, all breakeven prices were lower than or equal to €50, which is the current price of low-density chip genotyping in Denmark, Finland, and Sweden, so in the vast majority of cases, it is not profitable to genotype routinely for management purposes under the present price assumptions.
You can view the full report and author list by clicking here.