Cattle genetics aimed at beefing up environmental metrics

Important work carried out by Teagasc and the Irish Cattle Breeding Federation on genomic selection for beef cattle in Ireland could have a very positive impact on greenhouse gas emissions in this country.

The research has led to the development of a methodology to generate genomic proofs which can be used to improve the overall efficiency of cattle breeding, thereby reducing the overall environmental load of Ireland’s beef cattle.

"Cattle are big contributors to greenhouse gas emissions," says Teagasc research officer Dr Donagh Berry. "They are ruminant animals and the bacteria in their digestive systems leads to the production of a lot of methane. Cattle are responsible for 18 per cent of greenhouse gas emissions globally but in Ireland they are responsible for 33 per cent."

The higher level for Ireland is partly explained by the scale of the beef industry here. Ireland is the largest beef exporter in the northern hemisphere and the fourth largest in the world. That is naturally going to lead to an elevated proportion of greenhouse gas emissions from that source. Other factors come into play as well, however, and Berry’s work offers some solutions to them.

Subfertile cows

Part of the problem lies in an unintended consequence of selective cattle breeding over many years. “When we were breeding cattle we were selecting for bigger, more muscular animals,” Berry points out. “But this can impact negatively on other traits.”

According to Berry many Irish cows are termed as subfertile as a result of this practice. With the cow devoting much of her energy to growth and putting on more muscle mass there is a compensatory effect where less energy is devoted towards other aspects such as the reproductive system. “We have been indirectly breeding subfertile cows,” he adds.

At present a beef cow in Ireland produces 0.79 calves a year on average. “For the rest of the time they are standing around doing nothing and producing greenhouse gases. If you could get 10 per cent of a million cows to produce an additional calf, that would be 100,000 animals not just producing greenhouse gases and it would contribute to the economy as well.”

He also notes that beef cows at present calve for the first time at 36 months while cattle should normally be ready to produce their first calf at 24 months. Bringing forward this first calving would also contribute greatly to efficiency.

The key lies in selecting cows for reproductive traits as well as growth. But this can be a long-term and quite hit-and-miss process if done using traditional methods. Berry explains that while the parentage of an animal gives some guide to how its progeny will turn out there are no guarantees.

“For example, the variability or standard deviation of human height in a population is about seven centimetres. You would think that two tall parents would produce tall children but that is not necessarily the case. The standard deviation for their children is 5.6cm – not too far off that for the population as a whole.”

Testing at birth

The issue with cattle is that you have to wait two years to see how the progeny of a sire or dam perform and a bull might have been used to impregnate 30,000 cattle in that time. “It can take up to six years and a lot of money to figure out if a bull is good or not.”

And that’s even when the DNA profile of the bull is known. The key is to find out as soon as possible if the animal is passing on positive traits to the next generation. This means moving to testing the calves at birth. This allows for better decision-making at that time in terms of which animals are selected for fattening up for the market and which will be used for breeding in future.

Ireland is only the second country in the world after Australia to launch multi-breed genomic selection for beef cattle and the research has the potential to bring enormous benefits to Ireland's beef sector. It was introduced to the dairy sector seven years ago and it is now used by 70 per cent of Ireland's dairy farmers.

“It is estimated that it has produced €630 million in returns to the dairy sector since 2009 and we are hoping for something similar in the beef sector,” Berry says.