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Grape by-product cuts dairy emissions by 20 per cent

Cow in feeding stall

Cow in feeding stall

Wine drinkers and dairy farmers have more in common than they think, with a by-product of the wine making process providing cattle with significant nutrition and environmental gains.

At a glance

  • Study at DPI Ellinbank found cows fed wine grape by-product decreased methane (CH4) emissions by 20 per cent.
  • Grape marc also substantially increased healthy fatty acids in milk.
  • 200,000 tonnes of wine grape by-product is produced in Australia every year, most of which goes to waste.

Feeding by-products from the wine making process to dairy cows can reduce methane emissions by 20 per cent, according to a new study.

Researchers fed cattle the stems, seeds and skins from wine grapes — known as grape marc — for just over a month and found that as well as slashing emissions the diet also improved the nutritional value of milk.

DPI scientist Peter Moate said this type of study had never been done before.

“This is the first experiment that I’m aware of in the world where people have fed grape marc to cattle and measured the methane response.”

The background

A cow consuming ensiled grape marc

A cow consuming ensiled grape marc

Dr Moate said the experiment culminates a three-year project into reducing methane emissions from dairy cows.

Methane is a potent greenhouse gas, 21 times more powerful than carbon dioxide in terms of its global warming potential.

“We’ve been investigating nutritional ways to reduce methane emissions from dairy cows. To date we’ve examined a number of feed supplements, including whole cotton seeds. Feeding whole cottonseed can reduce methane emissions by about 15 per cent,” Dr Moate said.

He said other supplements trialled included brewers’ grain, cold pressed canola and tannin from black wattle.

From a review of the scientific literature worldwide, Dr Moate has calculated that each one per cent increase in dietary fat consumption delivers methane emission reductions of 3.5 per cent.

Therefore, an increase in the dietary fat concentration of four per cent can result in a 14 per cent reduction in methane emissions, particularly in summer months when the fat concentration in pastures is lower than at other times of the year.

Introducing grape marc

Ensiled grape marc up close

Ensiled grape marc up close

Currently, 200,000 tonnes of grape marc are produced in Australia each year, mostly along the Murray irrigation areas.

The bulk of it is ploughed into the soil although a small amount is being used in feedlots.

As well as its plentiful supply, Dr Moate said grape marc appealed as a potentially useful dietary methane mitigant because it has a high concentration of fat and also a high concentration of tannins, both of which are known to reduce methane production in cattle.

Most people are familiar with tannins. They are the chemicals in red wine that give it an astringent taste.

The study, carried out at DPI Ellinbank, saw 32 cattle divided into three groups and fed different diets over 37 days.

The first was a control group and each cow in this group was fed a diet containing crushed wheat grain and lucerne hay, while the second group was fed a diet containing crushed wheat grain, lucerne hay and 5kg of dry matter (DM) of pelleted dried grape marc.

The cows in the third group were fed the control diet and 5kg/DM of ensiled grape marc. The dietary composition of the ingredients are shown in Table 1.

The ensiled grape marc was stored in sealed plastic bags to prevent it from rotting.

The cattle were milked twice a day over the 37 day study period.

TABLE 1 Composition (g/kg DM unless otherwise defined) of dietary ingredients
Parameter Crushed wheat Alfalfa hay Dry grape marc Ensiled grape marc
Crude protein 132 168 131 133
Soluble protein (% CP) 34 44 25 23
Acid detergent fibre 33 444 477 531
Neutral detergent fibre 114 514 507 535
Lignin 16 89 369 422
Non-fibre carbohydrate 731 216 183 177
Starch 557 8 6 3
Ash 14 101 85 77
TDN 85 53 53 48
Crude fat 24 27 142 126
Triglyceride 22 9.0 97 94

The results

Dr Moate said the results were amazing, with both groups fed grape marc achieving a 20 per cent reduction in methane emissions expressed in grams per day, with the same reduction in grams emitted per kilogram eaten (see Table 2).

TABLE 2 Influence of diet on methane (CH4) emissions
Parameter Control Dry grape marc Ensiled grape marc
Means in the same row followed by different letters differ significantly (P < 0.05). This means that in the first row, 375 a is not significantly different in a statistical sense from 389 a, but both 375 a and 389 a are statistically significantly different from 470 b.
CH4 (g/cow/day) 470 b 375 a 389 a
CH4 (g/kg DMI) 26.1 c 20.2 a 21.5 b
CH4 (g/L Milk) 35.3 b 26.1 a 35.2 b
Milk (L/d) 13.4 ab 15.0 b 11.5 a

And he said the benefits didn’t stop there.

“As well as substantially reducing emissions, it altered the fatty acid content of the milk.

“Grape marc contains a lot of unsaturated fatty acids, especially linoleic acid. By feeding grape marc to the cows we increased the concentration of unsaturated acid, polyunsaturated acid and reduced the concentrations of saturated acids in milk.” This is shown in Table 3.

TABLE 3 Means of fatty acid composition of milk (g/100g)
Parameter Control Dry grape marc Ensiled grape marc
Means in the same row followed by different letters differ significantly (P < 0.05). See above explanation.
Total saturated 78.90 c 59.23 a 71.53 b
Total monounsaturated 18.57 a 33.13 c 24.78 b

Total polyunsaturated
2.53 a 7.64 c 3.69 b
Total de novo 31.04 c 23.47 a 27.80 b

Dr Moate said the grape marc also substantially increased the concentrations of conjugated linoleic acid in milk, a fatty acid known to combat cancer, diabetes and arthritis.

This experiment was conducted with cows in late lactation. Dr Moate hopes to repeat the trial with cows in early lactation.

Who benefits?

Dr Peter Moate with a cow involved in the study

Dr Peter Moate with a cow involved
in the study

Snapshot

Project name: Reducing Emissions from Livestock

Project team: DPI: Peter Moate, Richard Williams, Bill Wales, Richard Eckard

Project funding: DPI, Dairy Australia, Meat and Livestock Australia, Gardiner Foundation, Federal Department of Agriculture, Fisheries and Forestry

Project website: DPI - Carbon and Emissions: Methane

Location: Ellinbank, near Warragul

Timeframe: 2009–2011

Contact: Peter Moate

Email: peter.moate@dpi.vic.gov.au

As well as providing winemakers with a ready outlet for their waste product, Dr Moate said grape marc represented a cost effective way for neighbouring farmers to improve their milk quality and help the environment.

Those further afield may struggle, however, as ensiled grape marc is bulky and expensive to transport and there are some transportation restrictions on ensiled forms of grape marc to prevent the spread of the grape disease phylloxera.

The big picture

Previously, researchers had looked at black wattle for its tannins, which in overseas research was found to reduce methane emissions by 15 per cent.

While DPI researchers were able to replicate these results, the cows were less impressed.

“It’s very bitter and cows don’t like to eat it, so it had to be drenched,” Dr Moate explained.

Feeding cattle a combination of black wattle tannin and cotton-seed oil was expected to provide an added decrease in emissions, but this failed to happen.

Meanwhile, algae meal being grown by Australian power plants as a way of using their captured emissions was also trialled.

“In vitro (test tube) studies in Europe have shown you can reduce methane emissions by 80 per cent.”

In the DPI study, however, no difference to emissions was achieved, although omega 3 levels in milk were enhanced.

Dr Moate said there was much scope to reduce emissions from cattle.

“I don’t think there will be a silver bullet that will reduce them completely. What we’re thinking is that there will be a number of approaches that when combined will substantially reduce emissions of methane,” he said.