Disappointing Setback in NZ Low-Emission Dairy Bulls Genetics Research

New Zealand's dairy industry has long pinned hopes on genetic breeding as a sustainable path to slashing methane emissions, but a landmark study has delivered a sobering blow. Researchers from Livestock Improvement Corporation (LIC) and partners found that low-emission traits observed in young bulls do not persist in their daughters once they begin lactating—the phase accounting for about 80 percent of a dairy cow's methane output. This revelation challenges the feasibility of rapid genetic selection for lower-emitting herds and underscores the complexities of enteric fermentation in ruminants.

The five-year program, launched in 2021, aimed to leverage the fact that a handful of elite bulls sire 85-90 percent of the nation's replacement heifers. By identifying and propagating low-methane genetics through artificial insemination, the industry sought a permanent, cumulative reduction without altering farm practices. Early results fueled optimism, but measurements on lactating daughters revealed no significant differences between offspring of high- and low-emitting sires.

New Zealand's agricultural sector contributes nearly half of the country's greenhouse gas emissions, with dairy farming responsible for around 26-30 percent of total emissions, predominantly methane from cow burps during digestion. Enteric methane, produced when microbes in the rumen break down feed, has become a focal point amid global pressure to curb short-lived climate pollutants. The government's biogenic methane targets—10 percent below 2017 levels by 2030 and up to 24-47 percent by 2050—place dairy at the forefront, prompting investments in science-led solutions.

Breeding for efficiency has historically boosted milk production while trimming emissions intensity. For instance, genetic gains have already reduced methane per kilogram of milk solids by improving feed conversion. However, gross emissions remain high due to herd expansion, making tools like low-methane genetics appealing for absolute cuts.

The study employed state-of-the-art GreenFeed chambers at facilities like LIC's Tauwhare farm near Hamilton. Young bulls, aged 6-9 months from LIC and CRV progeny tests, were fed standardized lucerne hay cubes. Devices captured breath samples multiple times daily, calculating methane yield per kilogram of dry matter intake (CH4/DMI)—a key metric to ensure reductions don't compromise appetite or output.

Annual cohorts of 200-240 bulls revealed 15-20 percent variation, with heritability around 10 percent—enough for selective breeding. Twenty-five high- and low-emitting sires were chosen to produce 400 heifers via Pāmu Farms. These daughters were tested as yearlings (8-10 months), showing promising inheritance. But in their first lactation, emissions aligned regardless of sire group.

This step-by-step validation highlighted a critical gap: traits expressed in growing animals fade under lactation demands, where rumen dynamics shift with higher energy feeds and milk synthesis.

LIC chief scientist Dr. Richard Spelman called the results 'disappointing,' noting, 'We don't want a low methane cow that doesn't eat much; we want one that eats a lot, produces lots of milk, but emits less per kilogram of dry matter.' Ag Emissions Centre executive director Naomi Parker echoed the sentiment but remained pragmatic: 'Genetics still can have a meaningful role in reducing gross methane emissions.' LIC CEO David Chin emphasized applying insights to dairy-beef programs and pairing genetics with other tools.

The setback tempers expectations but validates methane's genetic basis, paving the way for refined strategies like direct lactation phenotyping or genomic proxies from milk microbiomes and blood markers.

Contrast this with sheep, where AgResearch has triumphed. Over a decade, they've bred flocks emitting 10-15 percent less methane without productivity loss—leaner meat, more wool, and economic gains of $6-10 per ewe in breeding indexes. Portable AgPAC chambers enable on-farm selection, now exported globally. Beef cattle programs echo this success, suggesting dairy's challenges stem from lactation physiology rather than inherent unbreedability.

Massey University researchers contribute via NZAGRC, publishing on grazing cow methane factors (e.g., 21.6g CH4/kg DM default) and genetic correlations with traits like residual methane emissions.

🧬 Implications for New Zealand's Dairy Genetics Landscape

The findings pivot research toward lactating cow measurements—costlier but essential for DNA breeding values targeted by 2026. With LIC/CRV proving 90 percent of heifers, genomic tools could still deliver 1-2 percent annual gross reductions if heritability holds.

Universities like Massey and Lincoln play pivotal roles, training geneticists through veterinary and animal science programs. NZAGRC, a Massey-hosted consortium, coordinates such efforts, fostering PhD projects on rumen genomics and proxy traits.

Beyond genetics, alternatives abound. Feed additives like 3-nitrooxypropanol (3-NOP, Bovaer) inhibit methanogens by 20-30 percent, trialed in NZ pastures. Vaccines targeting rumen microbes aim for 30 percent cuts, with prototypes in sheep. Asparagopsis seaweed offers promise but supply hurdles persist. Efficiency breeding—higher milk solids per head—complements these, already slashing intensity 1 percent yearly.

Massey University's Institute of Veterinary, Animal and Biomedical Sciences leads dairy methane studies, from rumen microbe markers to grazing emission models. Recent papers quantify animal factors like metabolic weight influencing CH4 yield, informing breeding indices. Lincoln University focuses on sustainable systems, integrating genetics with pasture innovations.

These institutions produce experts for LIC/AgResearch, with programs like Massey's Animal Genetics MSc attracting global talent amid NZ's ag-tech boom.

Stakeholders urge diversified strategies: DairyNZ promotes 'four pillar' mitigation—genetics, supplements, farm systems, manure. Policymakers eye incentives for adopters, balancing food security with Paris commitments. Farmers face pressure but value science; surveys show 95 percent prioritize productivity alongside emissions.

Future research demands investment: proxy development (gut bugs, plasma biomarkers) for 10,000-animal scales, lactation-focused breeding values by late 2020s. International collaborations, like NZ-Ireland grazing studies showing lower-than-expected emissions, refine models.

For ag students, this underscores resilient careers—demand surges for geneticists tackling climate challenges.

Photo by Griffin Wooldridge on Unsplash

This study, while sobering, advances NZ's world-leading ag emissions platform. Genetics endure as a cornerstone, refined for dairy realities. Universities like Massey equip the next wave, ensuring innovation sustains the $18 billion dairy powerhouse.

Explore opportunities in NZ ag research at research jobs or NZ higher ed jobs.