A topic that kept repeating at the DairyNZ Farmers' Forum in Whangārei last week was the need to tighten the belch.

What the industry needed were highly fertile, high milkfat, low-farting dairy herds, but winning that trifecta would take a lot more science than putting a bull over a cow.

Around 100 farmers at the Future Prospects conference got the low-down on ''real science'' around fertility, milk yield, climate change and reducing methane emissions caused by cows' wind and excrement.

Possible solutions included genetically modified ryegrass pasture, feeding cows kitty litter and growing a grass ancient peoples touted as a magic cure-all but New Zealand farmers have always treated as a weed.

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A series of precis on development and research started with the controversial topic of genetically modified organisms, specifically a United States field study of HME (high-metabolisable energy) ryegrass, now in its third year of in-ground trials.

AgResearch scientist Greg Bryan said the expectation was that HME ryegrass would ''help [New Zealand] farmers manage the environmental effects of farming''.

Trials showed that higher photosynthesising HME ryegrass could store at least 3 per cent more fat in its leaf cells than conventional ryegrass, improve nutritional quality, reduce nitrogen excrements and decrease methane emissions.

''But it's not going to be a single solution,'' Bryan said.

Animal nutrition trials - the guts of the matter - were expected to start in 2021.

''Be under no illusion, this is GM technology,'' Bruce Thorrold, DairyNZ strategy and investment head, told the conference.

Bruce Thorrold, from DairyNZ, leading the Whangārei farming forum.
Bruce Thorrold, from DairyNZ, leading the Whangārei farming forum.

That GM status would make getting the crop into Northland and neighbouring anti-GMO districts problematic, but that was only one piece of a policy and trade-off puzzle.

''We're talking about a great market without GM, '' Thorrold said.

Members of the audience pointed out that ryegrass did not do well in Northland over summer.

''Why not look at heat-resistant varieties, especially with climate change? Why concentrate on something that's not relevant for Northland?''

Someone else asked if research was being done on kikuyu grass.

The audience heard about trials using synthetic zeolite, a manufactured form of the porous clay mineral zeolite (kitty litter), as a food supplement with methane inhibitor qualities.

However, it was not a practical solution in New Zealand where herds lived in paddocks because animals needed to ingest it every two hours.

Herd fertility, genetics and the cost of empty cows were other areas of research, and Thorrold said that rather than milk yield, ''the economics are driving us toward more fertility.''

Mark Aspin, general manager for the Pastoral Greenhouse Gas Research Consortium, spoke about ''tightening up our belch''.

''We know how the methane an animal produces is directly proportionate to the amount of feed.''

Methane inhibitors could one day include a vaccine that caused a cow to produce antibodies which reduced methane, he said.

It could also be that one day most of Northland's 300,000-plus cows ate plantain, used since the beginning of human history to make a soothing tincture, heal wounds, cure gastric upsets and calm allergies.

While plantain might not stop cows from farting, a 30 per cent pasture cover would reduce nitrate leaching, have positive effects on soil and bring about ''some'' greenhouse gas reduction, DairyNZ scientist David Chapman said.

''It could be a potent pasture-based solution to nitrate leaching.''

Against plantain was its tendency to pug on Northland's clay soils, where ryegrass holds its root system.

Fonterra would be involved in research into whether the active chemical compounds in plantain grass affected milk quality, composition or taste, Chapman said.

''We don't want to give anyone in China a fright.''

■ Northland: 308,587 cows and 138,040ha in dairy farming (2017).
■ New Zealand: 4.8 million cows and 1.7 million hectares.
■ Northland dairy export earnings $420 million, New Zealand $13.4 billion
(2017)