DNA: ‘What a success story agriculture has been’

“What a success story agriculture has been. The changes that we have made to plants and animals have been amazing. Humans are changing the world through agriculture.”

This was the opening message from Dr. Emma Finlay, a bioinformatician in the school of Biotechnology, Dublin City University (DCU), at the ‘DNA Tells Tales’ conference in Tallaght IT recently.

Emma started out by commenting on the role humans have played in genetics and improving quality and yield in both animal and tillage enterprises.

“It was the earliest humans who realised if you plant a crop of wheat, your very best grains shouldn’t be eaten and these should be used as seeds the following year.

The changes that we have made to animals has been huge and this has only intensified in modern years.

She used poultry enterprises as an example, stating: “Modern birds are four times heavier; their breast meat is more than twice the percentage of what it used to be. This is as a result of intensive selection for meat production.”

Emma – who has also carried out research for Teagasc in Grange, Co. Meath – made reference to the dairy industry and how much it has changed over the years in relation to milk production – something which is very apt at this moment in time.

“Looking at cows in the 1970s, they would produce 12L/day. Nowadays, a cow can produce anything up to 24.5L/day.

“The rate of milk production increased about 6% per year in Ireland for decades. We had one of the fastest rates of increase in this area. This has all come about from quantitative genetics.”

Emma continued: “How do we know what bulls to breed from if we want cows with the maximum amount of milk? We measure a bull’s daughters.

“By doing this, we can see how much milk they give and calculate a breeding value for that bull based on that information. As a result, we know that this bull has good or bad traits for milk production.

She outlined that this can be measured from his offspring or it can be based on information from his mother, father, brothers and all the pedigree of information that surrounds him.

This is where maths comes into play when calculating the breeding values.

“With the increase in DNA technology, the entire process has been sped up. Before, a bull would have to bought, reared and put to use. Only when his calves were born would we be able to check them for milk production.

“These days we can take a strand of DNA from a newborn calf and – because his DNA will not change with age – we will be able to tell what his offspring’s milk production will be,” she explained.

However, with this success story comes some negative impacts. Emma outlined how breeding for specific traits has lowered fertility levels because of a negative energy balance.

“This is because cows are working so hard to produce milk and get in-calf. There is a genetic link between the two.”

Bull fertility research

While carrying out research for Teagasc, Emma performed targeted next generation sequencing of defensin genes in Irish bulls of high and low fertility.

She prepared the libraries, captured the targeted genes, sequenced pooled samples and identified variants between genes.

Emma also discussed how she analysed the results for evidence of association between genetic variation and bull fertility and examined copy number variation among genes.

“Taking the different fertility levels in different breeds into consideration, we are definitely able to say that there is genetic variation in defensin genes across bulls,” she concluded.