Breeding for productivity – and the planet (Sept 2021)

Updated: 6 days ago


Two new genetic indexes are set to help producers breed more efficient and environmentally-friendly cows. And they’re set to play a key role in helping the sector to reach carbon-zero targets.


TEXT ANN HARDY



Genetics have key roles to play in improving the environmental efficiency of milk production. And AHDB Dairy’s launch of the EnviroCow genetic index will certainly help producers to breed more environmentally-friendly cows.


It is the first independent genetic index in the world to focus solely on breeding cows for their environmental credentials, incorporating cow lifespan, milk production, fertility, and another new index called Feed Advantage.


Launched with August’s bull proof run, EnviroCow is expressed on a scale of between -3 to +3, where the highest positive figures are achieved by bulls transmitting the best environmental credentials to their daughters. These are the cows predicted to emit lower levels of greenhouse gas (GHG) during their lifetimes for each kilogramme of solids-corrected milk they produce.


“This is a standardised scale rather than one that quantifies the exact carbon dioxide equivalent saved, as there are too many management variables influencing actual emissions,” says AHDB’s head of animal genetics Marco Winters. “These variables include the source of feed, which could be home-grown or imported, so a precise value is impossible to give.”


EnviroCow will be published for all dairy bull breeds and should be used alongside the main commercial breeding index, Profitable Lifetime Index (£PLI).


Carbon emissions


“We continue to recommend £PLI as the primary focus for genetic selection, but producers often drill down to different individual traits, to meet their herd and business goals. It’s increasingly likely they will have to monitor and reduce their carbon emissions for either their milk buyer, or to receive government subsidies, so breeding cows with better genetics for reduced GHG emissions will set them on the right track.”


Using sires with favourable scores for this index (around +3) will offer scope for genetic improvement, as well as making a dent in the industry’s carbon footprint. “Genetic selection can play a significant role in improving dairy cow efficiency. We have seen this in genetic traits selected for across many decades including milk, fat and protein production and, more recently, in numerous health and related traits, such as somatic cell count, mastitis resistance and fertility.” Mr Winters believes producers we can contribute to a reduction in CO2 equivalent of around 1% each year, for every kilogramme of milk produced. “This may not sound much in isolation but, as with all genetic gain, the effects are permanent and build up across generations,” he says.


Feed conversion


At the heart of EnviroCow is Feed Advantage, a genetic index that’s set to help producers breed animals that use the least amount of feed for their production needs. Identifying sires that transmit good feed conversion to their daughters, it is expressed as a predicted transmitting ability (PTA) in kilogrammes of dry matter intake (DMI) saved during each lactation. “The calculation of this index takes the feed an animal is expected to eat, given her solids-corrected milk production and the feed she needs for her maintenance, into account,” says Mr Winters. “This requirement is compared with her actual feed consumption – measured from individual cow intake data. And this identifies animals that are efficient feed converters.” Adjustments are also made for size, as smaller cows require less feed than larger cows giving the same level of milk production. “This means Feed Advantage represents the kilogrammes of dry matter saved due to both better feed conversion efficiency and lower maintenance costs,” he adds.


With the most efficient cows consuming as much as 400kg less in just one lactation than the least efficient cows, given the same level of production, there is substantial scope for reducing feed use. “Since feed represents around 70% of variable costs, this offers scope for financial as well as environmental savings,” says Mr Winters. “Even if you took a modest estimate of just a 100kg DMI benefit in every lactation, that’s 180,000 tonnes of dry matter saved each year across the nation’s 1.8 million dairy cows.”


Feed Advantage is the culmination of more than 30 years of research and data collection, from the Dumfries-based Langhill herd. Carried out by Scotland’s Rural College (SRUC), the studies measured, among other parameters, cows’ dry matter intakes throughout their entire lives.


Performance was then compared with the animals’ DNA, identifying patterns or SNPs (single nucleotide polymorphisms) associated with feed intake. Using this information, genomic indexes can be calculated, meaning every Holstein bull and cow which has been genomically tested will gain a PTA for Feed Advantage. “Coupled with better management, these indexes can reduce the use of the world’s finite resources – and the UK dairy sector’s carbon footprint,” adds Mr Winters.




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