Adding a negative economic value for methane could facilitate a substantial reduction in methane emissions while maintaining an increase in milk production, according to a new international study on dairy cows and breeding.
The study, published in recent days on the Journal of Dairy Science, highlighted that selecting cows that emit lower levels of methane is “one of the best approaches to reduce methane”, given that “genetic progress is permanent and cumulative over generations”.
The research report – titled “Breeding for reduced methane emission and feed-efficient Holstein cows: An international response” – was written by a selection of authors from across the world, including Denmark, Australia, Canada and Switzerland.
According to the study, data from different countries could be combined to accelerate the development of “accurate genetic parameters for methane traits” – and build a future genomic reference population.
Among its stated aims, the report sought to estimate “genetic parameters of seven suggested methane traits as well as genetic correlations between methane traits and production, maintenance, and efficiency traits using a multi-country database”.
Across the authors’ four countries, the study examined 15,320 methane production records from 2,990 cows.
A number of traits were examined, including dry matter intake; body condition score; various body weight metrics; milk yield; methane yield; methane intensity; “standardised methane production; residual feed intake; “energy corrected milk”; and three definitions of residual methane production.
Of these, according to the report, selection index calculations showed that residual methane had the most potential for inclusion in the breeding goal when compared with methane production, methane yield and methane intensity.
This, the authors say, was because “residual methane allows for selection of low methane emitting animals without compromising other economically important traits”.
“Residual methane” in the research was defined as the “residual of the partial regression of the methane production on MBW [metabolic body weight] and DMI [dry matter intake]”.
Other definitions used included “the residual of the partial regression on MBW and ECM [energy corrected milk]” and “the residual of the partial regression on MBW, DMI and ECM, along with fixed effects”.
In addition, the report said:
“Inclusion of residual feed intake in the breeding goal could further reduce methane, as the correlation with residual methane is moderate and elicits a favourable correlated response.
“Adding a negative economic value for methane could facilitate a substantial reduction in methane emissions while maintaining an increase in milk production,” the international study stressed.