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return to Farmers
Independent Weekly
March
4, 2004
Feeding
practices can reduce methane production from cattle operations!
by
Dinah Boadi and Karin Wittenberg, Department of Animal Science
Blame
bacteria. Without them, the world would be a much sweeter
smelling place! Bacterial fermentation of feed in the gut
of beef and dairy cattle produces methane (CH4) gas the animals
expel into the air. This methane isn't just a bad smell, it's
lost feed energy that could have been used to produce meat
or milk. On average, about 2-12% of the total feed energy
consumed by cattle can be lost as CH4 gas. One gram of CH4
gas is equivalent to 55.2 kJ of feed energy lost.
Methane
production from cattle and other ruminants also contributes
about 20% of atmospheric greenhouse gas (GHG) emissions associated
with global warming. Canada's estimates of CH4 emissions from
animal digestion increased about 10.6% from 1990 (15,994 kt
carbon dioxide equivalents/yr) to 2000 (17,696 kt carbon dioxide
equivalents/yr) due to growth of the cattle industry. Identifying
feeding practices that can reduce this methane production
by cattle will improve feed utilization and address environmental
concerns.
In general, when animal production efficiencies are improved
(through proper nutrition, management, reproduction or genetic
selection of animals), the amount of feed required to maintain
an animal is reduced by the diversion of more feed energy
to production. As a result, there's a drop in CH4 per unit
of meat or milk produced. If fewer animals can be maintained
in the herd with improved productivity, then the total amount
of CH4 produced from the overall herd can also be lowered.
Strategies
recommended to improve productivity include a) testing feed
and formulating balanced rations to suite the stage of production
of animals; b) managing bunk feeding to prevent under or overfeeding
of animals; c) maintaining proper health, efficient reproductive
and genetic selection programs; and d) using production enhancing
agents such as implants. Improved animal productivity has
been reported to reduce CH4 production per unit
of product by 25-30%.
Use of high quality forages, such as immature forages and
legumes can increase feed efficiencies and reduce CH4
production (% of energy intake) by about 20% or more in forage
based feeding programs. This is possible because the carbohydrate
fraction in young immature plants and legume species is more
readily digested in the gut. Rapid breakdown of plant carbohydrates,
coupled with a faster passage of digested feed from the forestomach,
causes a shift in the fermentation pattern towards lowered
methane gas production.
Grinding or pelleting low quality forages to improve utilization
by cattle can decrease CH4 production per unit
of feed intake by 20-40%. This can be explained to be due
to lowered fiber digestion and faster passage through the
digestive tract.
Preservation
of forages as silage vs. processing as hay is also associated
with lower CH4 emissions by animals because some
carbohydrates are fermented in the silo, reducing the extent
of fermentation in the animal's gut. One study demonstrated
a 33% depression in fermentation when cattle shifted from
alfalfa silage to alfalfa hay. It was also observed that the
addition of innoculant-enzyme preparations during ensiling
shifted fermentation patterns toward increased propionate
production and less CH4 production.
With the
current Canadian trend to include high proportions of forages
in beef and dairy diets, producers need to pay close attention
to the quality of forages related to intake and utilization
by animals. Implementing proper grazing management practices,
such as rotational grazing, early season grazing and inclusion
of legumes in grass pastures, will improve feed intake and
reduce animal-source methane.
For example,
research in Manitoba showed that CH4 production (% energy
intake) from grazing beef cows on alfalfa-grass pastures was
25% less than the production of beef cows grazing grass-only
pastures. Also, grazing steers early in the season reduced
CH4 production by about 29-45% compared to grazing steers
at mid and late seasons.
Ionophores, such as monensin and lasalocid which are added
to cattle diets to improve the efficiency of feed utilization,
can also reduce CH4 production. In our trials, monensin added
to dairy cows' diet at 24 ppm decreased CH4 production by
21% from control levels, and also increased milk production
to 31.5 from 27.6 kg /head/d. However, it has been confirmed
that the CH4 suppression that accompanies ionophore use is
not long lasting, as microorganisms in the gut may adapt to
ionophores over time. We are currently studying the results
of combining different ionophores in an effort to avoid microbial
adaptation.
Adding fats or oils to diets of high production animals also
decreased animal-source methane gas. This approach increases
the energy density of the diet and provides alternate hydrogen
acceptors which discourages the production of CH4 in the animal's
rumen. Feedlot trials have shown that daily CH4 production
can be reduced by 33% when 4% canola oil is added to a diet
containing 85% concentrate. Of course, too much of a good
thing can be bad - fats added in excess of 5-6% of the ration
dry matter can depress fiber digestion, thereby reducing intake
and production efficiencies.
So far,
we can't reduce cattle methane emissions to zero but producers
who choose the best strategy for their operations should be
able to cut methane by 25 to 40%. And that ought to put more
money in the jeans and less methane in the air!
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