Breeding for reduced methane emission and feed-efficient Holstein cows: An international response

Abstract

Selecting for lower methane (CH 4 ) emitting animals is one of the best approaches to reduce CH 4 given that genetic progress is permanent and cumulative over generations. As genetic selection requires a large number of animals with records and few countries actively record CH 4 , combining data from different countries could help to expedite accurate genetic parameters for CH 4 traits and build a future genomic reference population. Additionally, if we want to include CH 4 in the breeding goal, it is important to know the genetic correlations of CH 4 traits with other economically important traits. Therefore, the aim of this study was first to estimate genetic parameters of 7 suggested methane traits, as well as genetic correlations between methane traits and production, maintenance, and efficiency traits using a multicountry database. The second aim was to estimate genetic correlations within parities and stages of lactation for CH 4 . The third aim was to evaluate the expected response of economically important traits by including CH 4 traits in the breeding goal. A total of 15,320 methane production (MeP, g/d) records from 2,990 cows belonging to 4 countries (Canada, Australia, Switzerland, and Denmark) were analyzed. Records on dry matter intake (DMI), body weight (BW), body condition score, and milk yield (MY) were also available. Additional traits such as methane yield (MeY; g/kg DMI), methane intensity (MeI; g/kg energy-cor-rected milk), a genetic standardized methane production, and 3 definitions of residual methane production (g/d), residual feed intake, metabolic BW (MBW), BW change, and energy-corrected milk were calculated. The estimated heritability of MeP was 0.21, whereas heritability estimates for MeY and MeI were 0.30 and 0.38, and for the residual methane traits heritability ranged from 0.13 to 0.16. Genetic correlations between different methane traits were moderate to high (0.41 to 0.97). Genetic correlations between MeP and economically important traits ranged from 0.29 (MY) to 0.65 (BW and MBW), being 0.41 for DMI. Selection index calculations showed that residual methane had the most potential for inclusion in the breeding goal when compared with MeP, MeY, and MeI, as residual methane allows for selection of low methane emitting animals without compromising other economically important traits. Inclusion of residual feed intake in the breeding goal could further reduce methane, as the correlation with residual methane is moderate and elicits a favorable correlated response. Adding a negative economic value for methane could facilitate a substantial reduction in methane emissions while maintaining an increase in milk production.

Estimating methane coefficients to predict the environmental impact of traits in the Australian dairy breeding program

“…Methane introduces new challenges when implementing this approach as the analysis relies on many small data sets using different measurement techniques, introducing additional error. As methane for each country must be considered an independent trait, multitrait models are used which increases computational complexity (Manzanilla-Pech, 2021).…”

“…It is expected that a direct CH 4 EBV may become available in the near future (Manzanilla-Pech et al, 2021;Richardson et al, 2021b). In Australia, a residual methane trait that corrects for production and intake is most likely to be implemented (Richardson et al, 2021b).…”

“…In Australia, a residual methane trait that corrects for production and intake is most likely to be implemented (Richardson et al, 2021b). However, due to the limitation of data (n = 420, Richardson et al, 2021a) and challenges associated with combining data sets (Manzanilla-Pech et al, 2021), it is expected that the accuracy of genomic predictions will be low (González-Recio et al, 2020). Therefore, the optimal method to reduce emissions may be to develop a subindex comprised of a direct methane trait and the traits shown to have the largest effect on emissions, weighted using the coefficients estimated in the current study.…”

“…Methane is associated with DMI as 90% is generated as a by-product of feed fermentation, with 6% to 11% of the energy in feed being lost to the production of CH 4 (Appuhamy et al, 2016). The genetic correlation between CH 4 and DMI has been previously estimated between 0.3 and 0.6 (Difford et al, 2020;Richardson et al, 2021b;Manzanilla-Pech et al, 2021), suggesting that the genetic architecture of these traits is similar. However, the relationship between the general selection criteria for methane emissions and feed efficiency, of which CH 4 and DMI are component traits, is contested in dairy cattle (Løvendahl et al, 2018;González-Recio et al, 2020).…”

Animal as the Solution: Searching for Environmentally Friendly Dairy Cows

“…Numerous in-depth reviews have been conducted on management strategies in the existing literature to reduce enteric CH 4 production with a focus on animal genetic merit [86][87][88][89]. Multiple genetic pathways exist for reducing CH 4 production, from directly breeding for animals that produce less CH 4 , to diluting the CH 4 emissions by breeding for animals that are more efficient, thus emitting less CH 4 per product produced.…”