Tests on 400 heifers found that low-methane traits did not persist into lactation.
By Gianina Schwanecke of RNZ
New research looking at whether low-emitting bulls pass these traits onto their milking daughters has suffered a “disappointing” setback.
The Livestock Improvement Corporation - or LIC - and Ag Emissions Centre just completed the latest phase of a five-year methane research programme, initiated in 2021 and supported by CRV, to identify low-emitting bulls.
The hypothesis was that these bulls would pass the trait on to their milking daughters.
About 80% of methane emissions in dairy comes from lactating cows, as this is where most of the feed is consumed.
LIC chief scientist Dr Richard Spelman explained that, as a relatively small number of bulls sire the next generation of dairy cows, this approach offered a cost-effective and innovative way to introduce low-methane emissions into the national herd.
“One advantage we have in our industry, between LIC and CRV, we generate 85% to 90% of the replacement heifer calves,” he said.
“So what we were hoping to do, could we measure this trait in a young bull, and between LIC and CRV we buy about 300 bulls per annum - and if we could bring those animals in, measure their traits for methane, then that would be a very efficient way of working out what are the best genetics for the industry.”
The team started by identifying high- and low-emitting sires and chose 25 from each to breed 400 heifers, which were then measured at eight to 10 months of age.
He said early findings were “encouraging”, with lower methane emission traits identified in young bulls and clear evidence that these traits were passed on to their growing daughters.
“What we are trying to find is which animals actually produce less methane per kilogram of dry matter eaten.
“We don’t want to have a low-methane cow that doesn’t eat much; we want a cow that still eats a lot, produces a lot of milk, but the amount of methane she emits per kilogram of dry matter eaten is lower.”
However, this was not the case for lactating cows after the heifers were tested this milking season.
“The results we have to date have shown that there is no difference, or no significant difference, between the high and low-methane cows when they’re lactating.
“That has been a little disappointing for us.
“Obviously, the hypothesis we had - we could measure it in a young bull, very efficient, and that could be the way of getting that information and disseminating genetics into the industry - hasn’t come to fruition.”
Spelman said the work had confirmed the methane variation was related to genetics, so there was still scope to use it as a tool for reducing emissions. An advantage over other tools like boluses and vaccines gwas that it didn’t require a change to farm operations, as many farmers already used artificial insemination with their herds.
He said more investment in research was needed to continue studying a larger volume of cows to better understand such variations.
LIC chief executive David Chin said the insights gained were currently being applied within its dairy beef breeding programmes.
“Alongside sector partners, LIC remains committed to supporting efforts to reduce emissions intensity through breeding more efficient cows.
“The role genetics may play in reducing gross emissions is one of several possible solutions we will continue to explore.”
Ag Emissions Centre executive director Naomi Parker said while the outcome was disappointing, the findings were still valuable, and the job now was to shape the direction for future research.
“Genetics still can have a meaningful role in reducing gross methane emissions.
“For beef and sheep, we are still confident in the approach, and we will be feeding the insights from this trial into work underway in these areas.
“For dairy, we will consider taking a different approach that will likely focus on measuring lactating cows for methane production to generate a DNA-based selection criteria.”
- RNZ