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Nutritional management for enteric methane abatement: A review

  • Agriculture and Agri-Food Canada, Canada, Lethbridge

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A variety of nutritional management strategies that reduce enteric methane (CH4) production are discussed. Strategies such as increasing the level of grain in the diet, inclusion of lipids and supplementation with ionophores (> 24 ppm) are most likely to be implemented by farmers because there is a high probability that they reduce CH4 emissions in addition to improving production efficiency. Improved pasture management, replacing grass silage with maize silage and using legumes hold some promise for CH4 mitigation but as yet their impact is not sufficiently documented. Several new strategies including dietary supplementation with saponins and tannins, selection of yeast cultures and use of fibre-digesting enzymes may mitigate CH4, but these still require extensive research. Most of the studies on reductions in CH4 from ruminants due to diet management are short-term and focussed only on changes in enteric emissions. Future research must examine long-term sustainability of reductions in CH4 production and impacts on the entire farm greenhouse gas budget.
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CSIRO PUBLISHING Review Australian Journal of Experimental Agriculture, 2008, 48, 21–27
Nutritional management for enteric methane abatement:
a review
K. A. Beauchemin
, M. Kreuzer
, F. O’Mara
and T. A. McAllister
Agriculture and Agri-Food Canada, PO Box 3000, Research Centre, Lethbridge, Alberta T1J 4B1, Canada.
ETH Zurich, Institute of Animal Science, Universitaetstrasse 2, Zurich 8092, Switzerland.
Teagasc, Head Office, Oak Park, Carlow, Co. Carlow, Ireland.
Corresponding author. Email:
Abstract. A variety of nutritional management strategies that reduce enteric methane (CH
) production are discussed.
Strategies such as increasing the level of grain in the diet, inclusion of lipids and supplementation with ionophores
(>24 ppm) are most likely to be implemented by farmers because there is a high probability that they reduce CH
in addition to improving production efficiency. Improved pasture management, replacing grass silage with maize silage
and using legumes hold some promise for CH
mitigation but as yet their impact is not sufficiently documented. Several
new strategies including dietary supplementation with saponins and tannins, selection of yeast cultures and use of fibre-
digesting enzymes may mitigate CH
, but these still require extensive research. Most of the studies on reductions in
from ruminants due to diet management are short-term and focussed only on changes in enteric emissions. Future
research must examine long-term sustainability of reductions in CH
production and impacts on the entire farm greenhouse
gas budget.
Globally, ruminant livestock produce 80 million tonnes
of methane (CH
) annually accounting for 28% of
anthropomorphic emissions. Methane production is a natural by-
product of anaerobic respiration and its production serves as the
principal electron sink within the rumen. Methane represents
a significant loss of dietary energy, thus reducing enteric
production may also improve feed efficiency. Several
comprehensive reviews of the nutritional effects on enteric CH
production have been published (e.g. Johnson and Johnson
1995; Boadi et al. 2004; Monteny and Chadwick 2006) and
various models have been developed to predict CH
based on diet composition (e.g. Blaxter and Clapperton
1965; Moe and Tyrrell 1979; Pelchen and Peters 1998).
Although it is well recognised that diet composition affects the
contribution of ruminants to greenhouse gas (GHG) production,
the Intergovernmental Panel on Climate Change, which is
responsible for developing methodologies for estimating global
emission inventories, only differentiates between diets that
contain >90% concentrate and others (CH
conversion rate
as a percentage of gross energy intake; Y
=3%v. 6.5%)
(IPCC 2006). This decision was based on the high variability
in CH
emissions that have been measured from ruminants
even after implementation of nutritional mitigation strategies.
Our review discusses the nutritional management opportunities
for reducing enteric CH
emissions from ruminants that are
either commercially available or near market-ready. As such,
the review focuses mainly on the in vivo data available for each
abatement strategy and indentifies future research needs
and opportunities.
Nutritional strategies with a high probability
of reducing enteric CH
Replacing roughage with concentrate
It is well established that increasing the level of concentrate in
the diet reduces the proportion of dietary energy converted to
(Blaxter and Clapperton 1965), mainly due to the associated
change in fermented substrate from fibre to starch and the decline
in ruminal pH. In addition to reducing enteric CH
relative to dry
matter intake (DMI), concentrate feeding also improves animal
performance. However, substantial increases in concentrate
use would be difficult, or even impossible, to implement in
many areas of the world. The scope of using concentrates
to lower CH
emissions from the dairy sector is limited as
milk quality is negatively affected once concentrates exceed
50% of the diet. Furthermore, increased dietary concentrate
may sometimes increase total net emissions as more grain
must be grown, processed and transported, leading to increased
use of pesticides, fertilisers, and additional ancillary sources
of emissions associated with production and transportation
Lovett et al. (2006) examined both on- and off-farm GHG
emissions from production systems in which concentrate feeding
was increased from 376 (low) to 810 (medium) or further to
1540 (high) kg/cow.lactation. Total on- and off-farm emissions
were 1.15, 1.10 and 1.04 kg CO
equivalent per kg of milk
for the low, medium and high concentrate levels, respectively.
Between the extremes, there were decreases of 9.5%, 16% and
5% in emissions of CH
O and CO
, respectively. These
reductions may be slightly overestimated as Lovett et al. (2006)
© CSIRO 2008 10.1071/EA07199 0816-1089/08/020021
22 Australian Journal of Experimental Agriculture K. A. Beauchemin et al.
did not account for a possible increase in CH
emissions from
manure (Hindrichsen et al. 2006). The cost of implementing
this measure depended on the genetic production level of
the cows. With low or medium genetic merit cows (7053
and 7578 kg milk/305-days lactation, respectively), there was
an overall greater cost associated with increasing concentrate
levels, whereas it was profitable to implement the higher
concentrate level with high producing cows (8033 kg milk/305-
days lactation).
Johnson et al. (2002b) compared whole farm GHG
inventories (including emissions from fertiliser synthesis,
insecticide synthesis and application, fossil fuel use for cropping,
irrigation, transportation and processing) on dairies in California
and Wisconsin, USA, and in New Zealand. Forages made up
43, 61 and 96% of total DMI, respectively. Total farm GHG
emissions increased as forage proportion increased (1.26, 1.38
and 1.62 kg CO
equivalent per kg of milk), agreeing with the
comparison of Lovett et al. (2006).
The implication of these studies is that there are situations
where increased concentrate feeding both reduces GHG
emissions and increases farm profitability resulting in a win-win
situation. However, because so many factors affect overall farm
emissions, careful assessments of individual systems are needed
to confirm that increasing the proportion of dietary concentrate
would result in a net reduction in greenhouse gases.
Adding lipids to the diet
There is an increasing body of literature to indicate that
supplementation of diets with lipids that are not protected from
ruminal digestion reduces enteric CH
emissions. Although
reductions in CH
40% are possible with high levels of lipid
supplementation (Machm
uller and Kreuzer 1999; Jordan et al.
2006a), reductions of 10–25% are more likely in commercial
practice. Generally, it is recommended that total fat should not
exceed 6–7% of the dietary DM otherwise a depression in DMI
may occur, negating the advantages of increased energy density
of the diet. Dietary lipid supplementation reduces CH
by decreasing ruminal organic matter fermentation, the activity
of methanogens and protozoal numbers, and for lipids rich in
unsaturated fatty acids, through hydrogenation of fatty acids
(Johnson and Johnson 1995).
The effectiveness of adding lipids to the diet to reduce
emissions depends on many factors including level of
supplementation, fat source, fatty acid profile, form in which
the fat is administered (i.e. either as refined oil or as full-fat
oilseeds) and the type of diet. To examine the relationship
between level of added fat (% of DMI) and the reduction in
emissions (g/kg DMI) for a range of fat sources and
diets, we created a dataset based on 17 studies with beef
cattle, dairy cows and lambs (Fig. 1). Over this broad range
of conditions, CH
(g/kg DMI) was calculated to be reduced
by 5.6% with each 1% addition of supplemental fat. After
accounting for the random effect of study, the level of added
fat explained 67% of the reduction in CH
emissions relative to
control treatments (e.g. diets that contained either rumen-inert
fat or no added fat). There was considerable variation in the
reductions observed among fat sources, with very high
reductions occurring in some studies for coconut oil (63.8%
reduction with 7% added oil; Machm
uller and Kreuzer 1999) or
% Reduction in CH
Added fat (% DMI)
Fig. 1. Summary of literature results for 33 treatment means showing the
effect of added fat from various sources on the percentage reduction in
methane (g/kg dry matter intake, DMI) relative to the control diet. The
solid line represents the regression accounting for the effect of study;
y = 5.562 (s.e. = 0.590) × percentage added fat; (r
= 0.67; P = 0.004). Data
for cotton seed/canola seed from Johnson et al. (2002a) were omitted from
the regression analysis because the lack of treatment effects were attributed
to methodology used to measure CH
. Data from C. Benchaar, J.-S. Eun,
S. M. McGinn and K. A. Beauchemin (unpubl. data); Beauchemin and
McGinn (2006); Beauchemin et al. (2007b); Johnson et al. (2002a); Jordan
et al. (2006a, 2006b, 2006c); Grainger et al. (2008); Lovett et al. (2003);
uller and Kreuzer (1999); Machm
uller et al. (2000, 2001, 2003a,
2003b); McGinn et al. (2004); Woodward et al. (2006).
myristic acid (58.3% reduction with 5% added fat; Machm
et al. 2003b).
Refined oils that are high in medium-chain fatty acids
(MCFA; i.e. C12 : 0 and C14 : 0), such as coconut oil, palm kernel
oil, high-laurate canola oil, or pure myristic acid are particularly
effective in reducing CH
, especially for high-concentrate diets
and low Ca diets (Machm
uller et al. 2003b). The primary
mechanism whereby MCFA reduce CH
is through the toxicity
they exhibit on rumen methanogens (Machm
uller et al. 2003b).
However, refined oils containing MCFA are unlikely to be
used commercially by livestock producers as a CH
strategy because of cost.
Of the available sources of long-chain fatty acids (LCFA),
oilseeds and animal fats are usually less expensive than refined
oils. However, oilseeds that are not substantially damaged during
mastication require mechanical processing before feeding to
ensure the free oil interacts with microbial populations. Although
pure oils might be more effective against CH
than the same
amount of lipid supplied via crushed oilseeds, oilseeds are
preferred because of less adverse side-effects on intake and
fibre digestibility. With LCFA sources, CH
emissions are partly
lowered through reduced fibre digestion (McGinn et al. 2004;
Beauchemin et al. 2007b) and decreased DMI (Jordan et al.
2006a, 2006b).
Fats increase the energy density of the diet, which can lead to
improved animal performance in some (Jordan et al. 2006b), but
not all situations (Lovett et al. 2003; Jordan et al. 2006c). The
negative effects of fat feeding are less substantial when low-fibre
Nutritional management for enteric methane abatement Australian Journal of Experimental Agriculture 23
diets are fed. Thus, for beef cattle, it may be desirable to use fat
supplements for CH
reduction during the finishing phase, which
is expected to account for 20–50% of lifetime emissions of cattle
(e.g. in North America). However, in many countries, cattle are
finished on pasture making lipid supplementation of the diet
difficult. With dairy cows, high levels of added fat can reduce
milk fat percentage and change its fatty acid profile. Thus, care
must be taken in choosing the appropriate fat source and level
of supplementation. Finally, most of the studies that evaluate
the effects of fat supplementation on CH
have not yet tested
whether the reductions in CH
are sustained over entire lactations
or finishing periods.
Use of ionophores
Ionophores such as monensin are antimicrobials that are
typically used in commercial beef and dairy cattle production
to modulate intake, control bloat, and improve efficiency of
meat and milk production (McGuffey et al. 2001). Monensin
can increase the acetate-to-propionate ratio of the volatile fatty
acids (VFA) in rumen fluid through increasing the flow of
reducing equivalents to form propionate. It may also decrease
ruminal protozoal numbers. These two mechanisms contribute
to the anti-methanogenic effects of monensin and possibly, other
Monensin is typically added to the diet as a premix or
provided via a slow release capsule inserted into the rumen. A
summary of the literature indicates that the effect of monensin
on lowering CH
production may be dose-dependent (Table 1).
In recent studies, providing a dose of <15 ppm had no effect on
production (g/day or g/kg DMI) in dairy cows (C. Grainger,
M. J. Auldist, T. Clarke, K. A. Beauchemin, S. M. McGinn et al.
unpubl. data; Waghorn et al. 2007) while a dose of <20 ppm
either had no effect on CH
production or reduced total CH
but not CH
per kilogram of DMI in dairy cows (Van Vugt
et al. 2005). Higher doses (24–35 ppm) reduced CH
(g/day by 4–10% and g/kg DMI by 3–8%) in beef cattle and
dairy cows (Sauer et al. 1998; McGinn et al. 2004; Van Vugt
et al. 2005; Odongo et al. 2007), with short-term decreases in
of up to 30% being reported when 33 ppm of monensin
was included in high or low forage diets (Guan et al. 2006). The
relatively high dose rates needed to reduce CH
correspond to
the levels typically fed commercially to improve feed efficiency
in beef and dairy cows.
Unfortunately, the inhibitory effects of ionophores on
methanogenesis may not persist over time (Johnson and Johnson
1995). Guan et al. (2006) recently reported that monensin
(33 mg/kg) lowered CH
emissions in beef cattle by up to
30%, but levels were restored within 2 months. In that study,
the effect of ionophores on CH
production was related to
Table 1. Effect of monensin on methane production
Within rows and the methane emissions variable, values followed by the same letter are not significantly different at P = 0.05. n.s., no effect of monensin on
methane emissions reported
Animals Diet Dose Days Methane emissions Reference
(mg/day) (mg/kg after Control Monensin Control Monensin
DMI) dose (g/day) (g/day) (g/kg DMI) (g/kg DMI)
Controlled-release capsules
Dairy cows Ryegrass pasture 166 11 30–90 328 313 n.s. 19.2 20.0 n.s. Waghorn et al. (2007)
Dairy cows Ryegrass pasture 320 29.6 11 179a 158b 16.9a 15.3b Van Vugt et al. (2005)
Non-lactating Ryegrass pasture 320 35.2 72 246a 223b 25.5 24.8 n.s. Van Vugt et al. (2005)
Dairy cows Ryegrass + white 320 17.5 23 330a 309b 17.5 16.9 n.s. Van Vugt et al. (2005)
Dairy cows Ryegrass + maize 320 18.1 58 350 356 n.s. 19.2 20.5 n.s. Van Vugt et al. (2005)
Dairy cows Ryegrass + grain 240 13 25, 85 341 365 n.s. C. Grainger et al.
(unpubl. data)
Dairy cows Ryegrass + grain 240 13 83 376 386 C. Grainger et al.
(unpubl. data)
Dairy cows Ryegrass + grain 240 13 75 309 306 n.s. 16.7 17.0 n.s. C. Grainger et al.
(unpubl. data)
Added to the ration
Dairy cows Grain and forage 385 24 8–28 572a 517b 38.6a 35.7b Sauer et al. (1998)
385 24 8–28 599 598 n.s. 34.9 33.7 n.s. Sauer et al. (1998)
(2nd time)
Dairy cows Grain and forage 473 24 monthly for 458.7a 428.6b 23.3a 22.4b Odongo et al. (2007)
6 months
Beef cattle High forage 246 33 19 166.2a 159.6b 22.6a 20.7b McGinn et al. (2004)
Beef cattle High grain 271 33 weekly for –27% for Guan et al. (2006)
16 weeks 2 weeks, 0
by week 6
Beef cattle High forage 240 33 weekly for –30% for Guen et al. (2006)
16 weeks 4 weeks, 0
by week 8
24 Australian Journal of Experimental Agriculture K. A. Beauchemin et al.
protozoal populations, which adapted to ionophores over time. In
contrast, Odongo et al. (2007) provides evidence that adaptation
to ionophores may not always occur; in their study monensin
lowered CH
production in dairy cows over a 6-month period.
The possible transient effects of monensin on CH
combined with increased public pressure to reduce the use of
antimicrobials in animal agriculture, suggests that monensin
is not a long-term solution to CH
abatement. Furthermore,
regulations prevent its use in Europe.
Nutritional strategies that may reduce enteric
production but which need additional research
to quantify the possible reduction and optimise
the strategy
Feeding maize and cereal silages instead of grass silage
Crops such as maize and whole crop small grain silages are
cultivated, conserved, and fed because they typically provide
high yields of dry matter, are readily digestible, and increase
animal intake and performance. There are three ways by which
these alternative forages can reduce CH
emissions. First,
the starch within the grain silages favours the production
of propionate rather than acetate in the rumen. Second, by
increasing voluntary intake, these alternative forage crops can
reduce the ruminal residence time of feeds hence restricting
ruminal fermentation and promoting post-ruminal digestion.
Third, when maize silage replaces grass silage, the increase in
voluntary intake combined with the increase in the energetically
more efficient post-ruminal digestion (relative to ruminal
microbial fermentation) improves animal performance, thereby
lowering CH
emissions per unit of animal product (O’Mara
et al. 1998). However, there is a need for animal studies that
directly compare grass silage with maize and other cereal
silages to quantify the reduction in CH
that might be achieved.
Furthermore, comparisons need to be done on entire farm
budgets to account for changes in GHG emissions other than
enteric CH
. It is not clear how silage quality or substitution
of maize or cereal silage for grass silage affects CH
under farm scale production systems.
Improved pasture management
Improving pasture quality is viewed as a means of reducing
emissions because animal productivity may be enhanced
(i.e. lowering CH
emissions per unit of animal product) with
less dietary energy lost as CH
due to reduced fibre content of
the sward. However, it has yet to be conclusively demonstrated
that improving pasture management of intensive, well managed
pastures will reduce CH
emissions. For example, Alcock and
Hegarty (2006) modelled the effect of pasture improvement on
Australian sheep farms and estimated only a small reduction
in CH
output per kilogram of liveweight. In that study,
pasture improvement was predicted to lead to an increase in
stock numbers mainly due to increases in forage availability.
Improvements in pasture quality may reduce CH
output if
stocking densities remain static, but could increase emissions
if such a practice led to increased stocking densities and a
larger livestock population. This possible means of reducing
emissions warrants further investigation as it has little
additional cost and farmers generally seek to improve pasture
management as a means of increasing animal productivity and
farm profitability.
Forage species and legume inclusion
The CH
emissions (g/kg DMI) from animals fed forage legumes
is usually (McCaughey et al. 1999; Waghorn et al. 2002), but
not always (Van Dorland et al. 2007) lower than emissions from
animals fed predominantly grasses. Lower emissions for animals
fed legumes are often explained by the presence of condensed
tannins (CT), lower fibre content, higher DMI and faster rate
of passage from the rumen. Furthermore, C4 grasses may yield
more CH
per unit of intake than C3 grasses (Ulyatt et al. 2002).
Although differences in CH
emissions reflect compositional
differences between grasses and legumes, maturity at the time
of harvest may be confounded with the impact of forage type
on CH
emissions. For example, Chaves et al. (2006) found that
enteric CH
emissions were higher in cattle grazing alfalfa as
compared with grass pastures because of the advanced maturity
of alfalfa. Accordingly, CH
emissions can increase as a result
of greater extent of fermentation of the forage in the rumen,
a response that also frequently leads to increased forage intake
and an improvement in animal productivity. For example, adding
the tropical legume Arachis pinotoi to a grass diet increased CH
emissions from an artificial rumen (Hess et al. 2003b) as a result
of improving nutrient degradability of the diet compared with
the N-limited tropical grass-only control diet. Consequently,
estimates of CH
emissions from grazing ruminants should be
expressed on the basis of intake or animal product.
Plant secondar y compounds
The potential of plant secondary constituents to reduce enteric
production has only been recently recognised. As such, very
extensive screening of a large range of plants and their secondary
compounds, such as saponins and tannins, is now underway in
several laboratories (e.g. Wallace 2004; Patra et al. 2006).
The CH
-suppressing effect of plants rich in saponins seems
to be particularly related to their anti-protozoal effects. Several
recent in vivo and in vitro studies provide evidence for CH
suppression for at least some saponin sources (Table 2), although
its seems that not all saponin sources are effective (e.g. Hess et al.
An even larger pool of plant sources of tannins exists, and
these are often tropical shrub legumes. Due to the lower risk of
toxicity, research has focussed on CT rather than on hydrolysable
tannins. Early indications of the ability of CT to suppress CH
were given by Hayler et al. (1998), who tested in vitro the rumen
fluid from sheep fed different CT plants. More recently, Carulla
et al. (2005) supplemented sheep diets with Acacia mearnsii
CT and reduced CH
emissions by 12%, an observation
confirmed in dairy cows by C. Grainger, M. J. Auldist,
T. Clarke, K. A. Beauchemin, S. M. McGinn et al. (unpubl. data).
Evidently some sources of CT are not effective in reducing CH
production, as shown for Schinopis quebracho CT in cattle by
Beauchemin et al. (2007a).
Some legume forages that contain CT also reduce CH
emissions (Table 2), but their future wide-scale use for CH
abatement is likely to be limited. Many CT-containing legumes
can be cultivated in several geographical regions of the
world, but they frequently lack the agronomic rigor of more
Nutritional management for enteric methane abatement Australian Journal of Experimental Agriculture 25
Table 2. Selection of plant species characterised by secondary compounds and shown to have potential CH
suppressing properties as a whole or as an extract in the animal (a) or in vitro (i)
Cited references are: A, Carulla et al. (2005); B, C. Grainger, M. J. Auldist, T. Clarke, K. A. Beauchemin, S. M. McGinn
et al. (unpubl. data); C, Hayler et al. (1998); D, Hess et al. (2003a); E, Hess et al. (2003b); F, Hess et al. (2004); G, Hu
et al. (2005); H, McMahon et al. (1999); I, Pen et al. (2006); J, Pinares-Pati
no et al. (2003); K, Tavendale et al. (2005);
L, Soliva et al. (2007); M, Waghorn et al. (2002); N, Woodward et al. (2004); O, Zeleke et al. (2006)
Saponins group of secondary compounds Tannin group of secondary compounds
Plant species Expt Reference Plant species Expt Reference
Acacia angustissima iL,OAcacia mearnsii aA,B
Camellia sinensis (tea) seed i G Agelaea obliqua iC
Sapindus saponaria fruit a, i D, E, F Calliandra calothyrsus iE
Sesbania sesban iL,OLeucaena leucocephala iC
Yucca schidigera iILotus corniculatus (birdsfoot trefoil) a J, N
Lotus pedunculatus (big trefoil) a, i J, M
Mangifera indica iC
Medicago sativa (lucerne) i K
Onobrychis viciifolia (sainfoin) a H
Phylantus discoideus iC
traditional forage sources. Furthermore, high concentrations of
CT can impede forage digestibility and therefore reduce animal
While the variability in response among saponin and tannin
sources may be viewed as a constraint, it also provides an
opportunity to select highly efficient sources. Research is
needed to find the balance between reducing CH
and the potentially anti-nutritional side-effects associated with
supplementation of plant secondary compounds.
Use of yeast feed additives
Yeast products based on Saccharomyces cerevisiae are
increasingly used in ruminant diets to improve rumen
fermentation, DMI and animal performance (3 to 4% increases
in milk yield and weight gain; Robinson 2007). Numerous
commercial products are available and these vary widely in both
the strain of S. cerevisiae used and the number and viability of
yeast cells present.
Few animal studies have examined the effects of yeast
on CH
(McGinn et al. 2004). However, based on in vitro
responses, Newbold and Rode (2006) proposed that through
strain selection, it may be possible to develop commercial
yeast products that reduce CH
output while promoting rumen
fermentation and fibre digestion. Increased bacterial numbers in
the rumen resulting from added yeast may alter the production
of hydrogen due to the partitioning of degraded carbohydrate
between microbial cells and fermentation products (Newbold
and Rode 2006).
Because yeast products are generally modestly priced and
already widely used in ruminant production, acceptance of a
-reducing yeast product would likely be high. However,
considerable research and development would be needed
to deliver such a product to the marketplace. Commercial
manufacturers are reluctant to invest in such products because
animal performance, rather than CH
abatement, is the primary
driver for product development.
Diet supplementation with enzyme feed additives
Enzyme additives currently used in ruminant diets are
concentrated fermentation products that contain fibre-digesting
enzymes such as cellulases and hemicellulases. There is
increasing evidence to suggest that when properly formulated,
enzymes can improve ruminal fibre digestion and the
productivity of ruminants (Beauchemin et al. 2003). Preliminary
evidence suggests that it may also be possible to develop
commercial enzyme additives to reduce CH
emissions. In
a recent in vitro study, a range of enzyme products were
examined (S.-J. Eun and K. A. Beauchemin, unpubl. data).
While some products had no effect on ruminal fermentation,
one candidate increased fibre degradation of corn silage by
58%, with 28% less CH
produced per unit of fibre degraded.
Furthermore, in a recent study with dairy cows, supplementing
a corn silage-based diet with an enzyme additive reduced CH
production (g/g DMI) by 8.8% (P = 0.13) (K. A. Beauchemin
and S. M. McGinn, unpubl. data). Enzymes that improve fibre
degradation typically lowered the acetate-to-propionate ratio in
rumen fluid (Eun and Beauchemin 2007), which is thought
to be the primary mechanism whereby CH
production is
decreased. While it is premature to recommend the use of feed
enzymes for CH
abatement, preliminary findings suggest that
the potential of enzyme additives for CH
abatement warrants
further research.
Conclusion and future direction
Despite extensive research to identify nutritional strategies that
reduce enteric CH
production, on-farm adoption is expected
to be slow and mainly limited to measures that improve feed
efficiency, such as increased use of grain, lipid supplementation
and use of ionophores. Other practices such as improved pasture
management, replacing grass silage with maize silage, and the
use of legumes hold promise for CH
mitigation, but their impact
is not yet well documented. Supplementation of diets with plant
extracts, yeast cultures, or feed enzymes may also have a role as
future strategies of CH
It is clear that farmers are unlikely to adopt these
measures unless there is positive economic impact on animal
production. Some strategies reduce emissions while increasing
farm profitability, but usually this is market-dependent and
regionally variable. Introduction of carbon-offset trading
26 Australian Journal of Experimental Agriculture K. A. Beauchemin et al.
programs may provide a means of encouraging the adoption of
mitigation strategies that are presently not economically viable.
Mitigation measures need to be assessed on a whole-farm basis
(i.e. all GHG, with all on-farm and related off-farm emissions
counted) and over a longer period, but to date only a
few approaches have been examined from this perspective.
Finally, very few studies have examined whether simultaneous
application of multiple dietary measures are additive. In
fact, it is likely that some strategies are non-additive, with
either no effect or a reduced effect once the second strategy
is applied.
We thank Chris Grainger for his assistance in summarising the data used to
prepare Fig. 1.
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... The lipid content of DDGS (120 g EE·kg −1 DM; Table 1) increased the crude fat content from 15 to 54 g EE·kg −1 DM for H and H + DDGS, respectively. As result of a meta-analysis, Beauchemin et al. [39] concluded that, for each 1% of lipid added in the diet, there was a 5.6% reduction in the production of enteric CH 4 (g·kg −1 DMI). Benchaar et al. [40] worked with dairy cattle fed increasing levels of DDGS in the diet (10, 20, and 30% of the DM replacing flaked corn and soybean meal) and found that enteric CH 4 yield decreased by 0.5 g·kg -1 DMI (0.5, 0.4, and 0.7 for 10%, 20%, and 30% of the DM, respectively). ...
... Benchaar et al. [40] worked with dairy cattle fed increasing levels of DDGS in the diet (10, 20, and 30% of the DM replacing flaked corn and soybean meal) and found that enteric CH 4 yield decreased by 0.5 g·kg -1 DMI (0.5, 0.4, and 0.7 for 10%, 20%, and 30% of the DM, respectively). The reduction observed in our experiment was higher, and closer to the prediction reported by Beauchemin et al. [39], who signaled considerable variation in the CH 4 reductions observed among fat sources. ...
... Several studies have reported decreases in enteric CH 4 emissions when cattle diets were supplemented with unprotected fat [41][42][43]. It has been argued that a decrease in CH 4 emissions is due to the reduction in organic matter fermented in the rumen and by the toxic effects on cellulolytic bacteria, methanogen activity, and number of protozoa [39,44]. ...
Full-text available
Livestock systems based on subtropical and tropical pastures are characterized by the low productivity of livestock due to the poor nutritional value of the forage (low nitrogen concentration and digestibility, and high fiber and lignin concentrations). These conditions lead to low productivity and, consequently, high absolute emissions of methane (CH4) per unit of product. Dry distilled grains with solubles (DDGS) are the main by-product resulting from ethanol production, and they are characterized by their high-energy fibrous and protein content, thus becoming an option for the supplementation of low-quality forage. This research investigated the effects of dietary DDGS inclusion on dry matter digestibility (DMD) and enteric CH4 emission. Eight adult sheep of 64 ± 8 kg live weight were used. The duration of the study was 54 days, divided into two periods (changeover design), which comprised a 17-day pre-experimental period and 10 days for experimental data collection. Animals were allocated to one of two treatments used: hay (H) as a control treatment, where animals were fed with Rhodes grass hay alone; and H + DDGS, where animals were fed with H supplemented with DDGS. CH4 emissions were estimated using the sulfur hexafluoride (SF6) tracer technique. Diets containing DDGS increased DMI by 22% (p < 0.05) and reduced daily CH4 emissions by 24% (g/d), the CH4 yield by 35% (g/kg DMI), and the average value of CH4 energy per gross energy intake (Ym) by 44%, compared to the control treatment (p < 0.05). The experiment demonstrated that supplementation with DDGS in low-quality roughage reduced daily CH4 emissions, yields, and Ym.
... Both supplementation options (CUBES and DES) resulted in lower MY and Y m compared to the CON diet, which could be attributed to the presence of tannins in DES and possibly a combination of both presence of lipids and higher OM digestibility of the CUBES diet. Tannins and lipids have both been shown to have inhibitory effects on enteric CH 4 production when present in ruminants' diets (Beauchemin et al., 2008). Tannins have been shown to bind to CP and fiber in the diet reducing their digestibility and hence substrate availability for conversion to CH 4 by methanogens (Grainger et al., 2009;Williams et al., 2020). ...
... The 9% reduction in MY for CUBES compared to CON was higher than the predicted 2.2 -3.5% when using equations available in literature (Beauchemin et al., 2008;Moate et al., 2011) based on the EE difference of 6.2 g/kg DM between the two diets. Moate et al. (2011), from a meta-analysis using data from experiments with dairy and beef cattle supplemented with lipidrich concentrates, observed a reduction of 3.5% in MY for every 10g/kg DM increase in dietary fat, while Beauchemin et al. (2008) in a similar review with cattle and sheep, reported a 5.6% reduction with the same magnitude of increase in dietary fat content. ...
... The 9% reduction in MY for CUBES compared to CON was higher than the predicted 2.2 -3.5% when using equations available in literature (Beauchemin et al., 2008;Moate et al., 2011) based on the EE difference of 6.2 g/kg DM between the two diets. Moate et al. (2011), from a meta-analysis using data from experiments with dairy and beef cattle supplemented with lipidrich concentrates, observed a reduction of 3.5% in MY for every 10g/kg DM increase in dietary fat, while Beauchemin et al. (2008) in a similar review with cattle and sheep, reported a 5.6% reduction with the same magnitude of increase in dietary fat content. The higher EE content in CUBES than in the other two diets could have triggered several mechanisms suppressing CH 4 production per unit feed intake, including reduction in fiber digestion and protozoal numbers in the rumen (McGinn et al., 2004;Beauchemin et al., 2008). ...
Full-text available
In Africa, cattle are often fed low quality tropical roughages resulting in low-yielding animals with high methane (CH 4 ) emission intensity (EI, g CH 4 /per unit of product). Supplementation with protein is known to improve the nutritive value of the otherwise low-quality diets. However, animal nutrition studies in East Africa that are accompanied by CH 4 emission measurements are lacking. Thus, an animal experiment was conducted to quantify the effect of supplementing cattle fed mainly on low-quality Urochloa brizantha hay (control diet; CON; crude protein (CP) = 7.4%) or supplemented with either a tannin-rich leguminous fodder, Desmodium intortum hay (DES) or a commercial dairy concentrate (CUBES) on voluntary dry matter intake (DMI), nutrient apparent total tract digestibility, nitrogen (N) retention, enteric CH 4 production and animal performance (milk and average daily gain). Twelve mid-lactating crossbred (Friesian × Boran) cows (initial liveweight = 335 kg) were used in a 3×3 (Period × Diet) Latin square design with each period running for four weeks. Compared to CON, DES decreased nutrient (DM, OM, CP) intake, apparent total tract digestibility and daily milk yield. In contrast, CUBES increased nutrient intake and animal performance compared to CON, while nutrients’ apparent total tract digestibility was not different, except for CP digestibility that increased. Compared to CON, DES and CUBES improved overall N retention by the animals as a proportion of N intake. The DES diet compared with CON and CUBES, shifted the proportion of N excretion via urine to the fecal route, likely because of its tannin content. Both DES and CUBES, compared to CON, reduced methane yield (MY, g CH 4 /kg DMI) by 15% and 9%, respectively. The DES diet reduced absolute enteric CH 4 emissions by 26% while CUBES increased emissions by 11% compared to CON. Based on the present findings, high supplementation levels (>50%) of Desmodium intortum hay is not recommended especially when the basal diet is low in CP content. Supplementation with lower levels of better managed Desmodium intortum forage however, need to be investigated to establish optimal inclusion levels that will improve animal productivity and reduce environmental impact of livestock in smallholder tropical contexts.
... The effect of lipids on the degradability, production, and compositional quality of milk depends on the source and level of inclusion (Jacob et al. 2012). The addition of polyunsaturated lipid sources could be an alternative to maintain an optimal ruminal pH, which contributes to the proliferation of cellulolytic bacteria, increasing the digestion of cellulose and the use of ammonia, thus a greater use of N in bovines would be expected (Beauchemin et al. 2008;Cieslak et al. 2012;Patra 2013). ...
... In the process of ruminal biohydrogenation of PUFAs, hydrogen is captured from the medium (Beauchemin et al. 2008), which could be an alternative in controlling the ruminal methanogenesis and maintaining an optimal ruminal pH (Cieslak et al. 2012;Patra 2013). Most bacteria, especially cellulolytic ones, can use ammonia for microbial protein synthesis. ...
Full-text available
The objective of this study was to determine the nitrogen balance of Holstein cows grazing on an intensive silvopastoral system (ISS) with wild sunflower (Tithonia diversifolia (Hemsl.) A. Gray) and kikuyu grass (Cenchrus clandestinus (Hochst. Ex Chiov) Morrone) or on a monoculture (MONO) of kikuyu grass, and supplemented with polyunsaturated fatty acids (PUFAs), in order to compare the efficiency of animal nitrogen use in both systems, which is important for sustainable animal production. A concentrate with three different lipid combinations was used: control concentrate (D1)-3% commercial saturated fat; concentrate 2 (D2)-1% soybean oil, 0.5% fish oil, and 1.5% of bypass fat rich in n-3 fatty acids; and concentrate 3 (D3)-2.5% soybean oil and 0.5% fish oil. The variables under study were analyzed during two rotations in a randomized complete block (RCB) design. The dry matter intake was evaluated by the marker's method, using chromium oxide as an external marker and indigestible dry matter as an internal marker. The production of milk, urine, and feces was measured for 5 days to quantify nitrogen (N). The urine volume was estimated using creatinine. Nitrogen consumption (grams/day) was similar for cows in both systems (p [ 0.05). A significantly higher excretion of N in the urine (p \ 0.05) was found in the cows of the MONO group. The percent apparent nitrogen digestibility was higher (p \ 0.05) in cows of the ISS group (75.68%) than in cows of the MONO group (73.95%). The N utilization efficiency was significantly higher (p \ 0.05) in cows of the ISS group (23.24%) than in cows of the MONO group (19.39%). Therefore, the ISS with wild sunflower and unsaturated fat supplementation could be a positive strategy to improve the nitrogen balance and the productive efficiency of dairy cows in highland tropical regions, reducing the losses of nitrogen to the environment and contributing to the sustainability of the dairy production systems.
... Several approaches used to control ruminal acidosis disorder involve using feed additives such as ionophores. Monensin (MON) is the most common ionophore used in ruminant diets that improve ruminal microbial fermentation [10]. Also, it manipulates the organic acids production by decreasing lactate production [11] and increasing propionate production [2]. ...
Full-text available
Background In recent years, researchers have become increasingly interested in developing natural feed additives that can stabilize ruminal pH and thus prevent or eliminate the risk of severe subacute rumen acidosis. Herein, 3 experiments were conducted using a semi-automated in vitro gas production technique. In the experiment (Exp.) 1, the efficacy of 9 plant extracts (1.5 mg/ml), compared to monensin (MON; 12 μg/ml), to counteract ruminal acidosis stimulated by adding glucose (0.1 g/ml) as a fermentable carbohydrate without buffer was assessed for 6 h. In Exp. 2, cinnamon extract (CIN) and MON were evaluated to combat glucose-induced acidosis with buffer use for 24 h. In Exp. 3, the effect of CIN and MON on preventing acidosis when corn or barley grains were used as substrate was examined. Results In Exp. 1, cinnamon, grape seeds, orange, pomegranate peels, propolis, and guava extracts significantly increased ( P < 0.05) pH compared to control (CON). Both CIN and MON significantly increased the pH ( P < 0.001) but reduced cumulated gas production ( P < 0.01) compared to the other treatments. In Exp. 2, the addition of CIN extract increased ( P < 0.01) pH value compared to CON at the first 6 h of incubation. However, no significant differences in pH values between CIN and CON at 24 h of incubation were observed. The addition of CIN extract and MON decreased ( P < 0.001) lactic acid concentration and TVFA compared to CON at 24 h. The CIN significantly ( P < 0.01) increased acetate: propionate ratio while MON reduced it. In Exp. 3, both CIN and MON significantly increased ( P < 0.05) ruminal pH at 6 and 24 h and reduced lactic acid concentration at 24 h compared to CON with corn as substrate. However, CIN had no effect on pH with barley substrate at all incubation times. Conclusions It can be concluded that CIN can be used effectively as an alternative antibiotic to MON to control ruminal acidosis when corn is used as a basal diet.
... This strategy involves harvesting tree foliage and collection of pods to offer as supplementary ration, especially during the dry season (Smith et al. 2005) reducing mortality of twin kids and improving goat performance in Zimbabwe. Other than tannins, fatty acids (FA) are also believed to reduce CH 4 production when incorporated in animal diets (Beauchemin et al. 2008(Beauchemin et al. , 2009Soltan et al. 2018). ...
Full-text available
The Southern Africa Development Community (SADC) region is not a major emitter of greenhouse gases (GHG). However, Sub-Saharan Africa is considered a potential future hotspot for GHG emissions because of its large livestock population dispersed across large arid lands, coupled with the inherent low digestible feeds in the region and consequently low productivity of livestock. In SADC, climate change is predicted to increase temperatures further reducing agricultural productivity. Therefore, there is incentive to reduce agriculture’s contribution to GHG emissions in the SADC region. Ruminant production, a mainstay of rural economy, is predicted to decrease because of diminished grazing due to reduced rainfall and feed quality. However, ruminants’ enteric methane (CH4) production contributes to GHG emissions. This review explores strategies for the SADC region to reduce CH4 by ruminants. As methanogenesis is an outcome of microbial activity, potential opportunities include selecting animals with inherent low CH4 production; altering ruminal microbial populations to those that do not yield CH4; enhancing feed digestibility by feeding additives which improve diet quality and alter the ruminal microbiome and using specific forages such as seaweed or duckweed that contain plant secondary metabolites that may decrease methanogen populations or methanogenesis. These strategies are considered in terms of their potential magnitude of CH4 mitigation, the practicality for their implementation in the SADC region and their suitability to be included in the grazing-based livestock industries in the SADC region.
... In the present study, alfalfa was of high quality, with the concentration of fiber fractions much greater and that of protein lower in lespedeza. Diets rich in fiber promote high numbers and activity of ruminal fibrolytic microbiota that produce acetate and hydrogen, possibly stimulating methanogenesis [7,63]. In accordance, the molar proportion of acetate increased with increasing dietary concentrations of lespedeza. ...
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Twenty-four Alpine doelings, initial 25.3 ± 0.55 kg body weight (BW) and 10.4 ± 0.11 mo of age, and 24 Katahdin ewe lambs, 28.3 ± 1.02 kg BW and 9.6 ± 0.04 mo of age, were used to determine effects of dietary inclusion of Sericea lespedeza (Lespedeza cuneata) hay on feed intake, digestion, growth performance, energy metabolism, and ruminal fermentation and methane emission. There were four periods, the first three 42 days in length and the fourth 47 days. Diets consumed ad libitum contained 75% coarsely ground hay with alfalfa (ALF), a 1:1 mixture of ALF and LES (ALF+LES), and LES (10.0% condensed tannins; CT). The intake of dry matter (DM) tended to be greater (p = 0.063) for Katahdin than for Alpine (4.14 vs. 3.84% BW; SEM = 0.110). The dry matter intake was similar among the diets (3.97, 4.10, and 3.89% BW for ALF, ALF+LES, and LES, respectively; SEM = 0.134). The digestion of organic matter (75.3, 69.3, and 65.5%; SEM = 0.86), neutral detergent fiber (61.7, 50.5, and 41.4%; SEM = 1.49), and nitrogen (78.8, 66.9, and 50.8% for ALF, ALF+LES, and LES, respectively; SEM = 0.92) decreased as the dietary concentration of lespedeza increased (p < 0.05). However, there was an interaction (p < 0.05) between the breed and diet in nitrogen digestion, with a greater value for goats vs. sheep with LES (54.4 vs. 47.3%; SEM = 1.30). The digested nitrogen intake decreased markedly with the increasing quantity of lespedeza (38.0, 27.5, and 15.7 g/day for ALF, ALF+LES, and LES, respectively; SEM = 1.26). The average daily gain was greater for Katahdin than for Alpine (p < 0.001; 180 vs. 88 g, SEM = 5.0) and ranked (p < 0.05) ALF > ALF+LES > LES (159, 132, and 111 g, respectively; SEM = 6.1). The ruminal methane emission differed (p < 0.05) between animal types in MJ/day (1.17 and 1.44), kJ/g DM intake (1.39 and 1.23), and kJ/g ADG (18.1 and 9.8 for Alpine and Katahdin, respectively). Regardless of the period and animal type, diet did not impact methane emission in MJ/day or relative to DM intake, BW, or ADG (p > 0.05). The digestible and metabolizable energy intakes, heat production, and retained energy were not affected by diet (p > 0.05). In conclusion, future research should consider the marked potential effect of CT of forages such as lespedeza on nitrogen digestion and associated effects on protein status and other conditions that may be impacted.
The major purpose of this study was to determine how varying doses of algae-derived pure β– glucan affected in vitro gas generation, volatile fatty acid (VFA) concentrations, methane production, and protozoa populations. Different doses of β–glucan [i.e., 0, 50, 100, 150, and 200 mg/kg feed (DM basis)] were applied to corn silage as experimental treatments. After 6 and 24-96 hours of incubation, the dose of 200 mg/kg of DM β–glucan reduced total gas production more than the other doses (P
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This study assessed the association between encapsulated nitrate product (ENP) and monensin (MON) to mitigate enteric methane (CH4) in vitro and possible effects on ruminal degradability, enteric fermentation characteristics, and microbial populations. Six treatments were used in randomized complete design in a 2×3 factorial arrangement with two levels of MON (0 and 2.08 mg/mL of buffered rumen fluid) and three levels of ENP (0, 1.5 and 3.0%). The substrate consisted of 50% Tifton-85 hay and 50% concentrate mixture (ground corn and soybean meal). ENP replaced soybean meal to achieve isonitrogenous diets (15% CP). No ENP×MON interaction was observed for any measured variable (P > 0.05) except for the relative abundance of F. succinogenes (P = 0.02) that linearly increased in diets with MON when ENP was added. The ENP addition decreased CH4 production (P < 0.01) without affecting (P > 0.05) truly degraded organic matter nor the relative abundance of methanogens. Hydrogen production was reduced with MON (P = 0.04) and linearly decreased with ENP inclusion (P = 0.02). We concluded that use of nitrate is a viable strategy for CH4 reduction, however, no additive effect of ENP and MON was observed for mitigating CH4 production.
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The effects of supplementing a tropical, low-quality grass hay (Brachiaria dictyoneura) with legume foliage (Cratylia argentea) or fruits of the multipurpose tree Sapindus saponaria on ruminal fermentation, methane release and nitrogen (N) utilization were evaluated. Six Swiss White Hill lambs were used in a 6 ✕ 6 Latin-square design with a 3 ✕ 2 factorial arrangement of treatments with measurements of energy metabolism being conducted using open-circuit respiratory chambers. Treatments consisted of three basal diets, either grass alone or legume : grass ratios of 1 : 2 or 2 : 1. These basal diets were supplemented (1 : 3) with a control concentrate or with a concentrate containing 250 g/kg dry matter of S. saponaria fruits. The apparent total tract digestibilities of organic matter (OM) and neutral-detergent fibre (NDF) were reduced and the proportionate crude protein (CP) losses through faeces were increased (P < 0·01) by supplementation with S. saponaria , and digestibilities of OM and NDF were linearly reduced (P < 0·001) with increasing legume proportion. Body energy retention, however, was similar in all diets. Along with CP intake, the proportionate CP losses through faeces decreased (P < 0·001) with increasing legume proportion which was associated with improved (P < 0·001) body protein retention and reduced (P < 0·1) fat retention. Ruminal fluid ammonia concentration was not significantly affected (P > 0·1) by the inclusion of S. saponaria in the concentrate, but increased linearly (P < 0·001) as dietary legume proportion was elevated. Supplementation with fruits of S. saponaria increased (P < 0·01) total bacteria count, and decreased (P < 0·001) total ciliate protozoa count by more than proportionately 0·50. Daily methane release was reduced (P < 0·01) by S. saponaria supplementation in all basal diet types. Although being not clearly affected on a daily basis, methane release relative to body protein retention decreased linearly (P < 0·05) with increasing legume proportion. The fact that interactions were mostly non-significant (P > 0·05) indicates that supplementation with S. saponaria fruits is a useful means to reduce methane emission from sheep given both tropical grass-based and grass-legume-based diets. Likewise, including legumes in N-limited tropical diets seems to represent an environmentally friendly way to improve animal productivity.
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In two in vitro experiments with the RUSITEC-apparatus, Brachiaria dictyoneura was tested alone and with legumes at dietary proportions of 1/3, 2/3, or 3/3 of Arachis pintoi (Expt 1) and 1/3 of Arachis pintoi, Cratylia argentea, or Calliandra calothyrsus (Expt 2). In Expt 2, all diets were evaluated with and without 80 mg/g diet of Sapindus saponaria fruits. In Expt 1, the stepwise replacement of the grass by A. pintoi curvi-linearly increased rumen fluid concentrations of ammonia, volatile fatty acids, bacteria, and protozoa. Methane release rates were 1.7, 7.3, 8.8, and 9.0 mmol/day. With increasing legume proportion, more organic matter and protein were degraded, the latter being only partially recovered as ammonia. In Expt 2, 1/3 of A. pintoi basically had the same effects as in Expt 1. Cratylia argentea was less effective in modifying the fermentation pattern. In association with a higher nutrient degradation and rumen ammonia concentration, C. argentea and A. pintoi increased methane release to about 3- and 4-fold levels. Calliandra calothyrsus reduced nutrient degradation and methane release per gram of organic matter degraded. Tannins, predominant in C. calothyrsus, might have affected methanogenesis. Sapindus saponaria reduced methanogenesis by 11% on average in grass-alone and legume-supplemented diets.
Methane is an unavoidable product of rumen fermentation. Reduction of rumen methanogenesis can lead to an improved exploitation of nutrient energy and a decrease of methane emissions in the environment. The objective of this study was to investigate the effect of several fat and tannin containing feedstuffs on the production of CH 4 and concommitant CO 2 using the in vitro system „Hohenheim Gas Test” (STEINGAß & MENKE 1986). Special emphasis was directed to the suitability of the method to measure the effect of various substrates on rumen methanogenesis. Another objective was to investigate to what extent increasing fat or tannin contents in the diet of the donor sheep affect methanogenesis in vitro.
Methane production has been measured from lambs fed contrasting forages. This work has been driven by the need to reduce greenhouse gas emissions from agriculture and to determine energy losses to methane from contrasting diets. Young ram lambs were fed either fresh ryegrass/white clover pasture, lucerne (also pelleted lucerne), sulla, chicory, red clover, Lotus pedunculatus (lotus) and mixtures of sulla and lucerne, sulla and chicory and chicory with red clover. The effects of condensed tannin (CT) in lotus on methane production were also measured. The trials were carried out indoors with sheep held in metabolism crates to enable an accurate measurement of intake and digestibility as well as methane production. Principal findings were a two-fold range in emissions from 11.5g CH4/kg dry matter intake (DMI) with lotus to 25.7g CH4/kg DMI with pasture and a 16% reduction in methane production due to the CT in lotus. This range in emissions from good quality forages represents a loss of about 7-11% of metabolisable energy and presents a clear direction for future research to better utilise the feeding value of pastures and reduce greenhouse gas (GHG) emissions from agriculture. High quality perennial forages should be used where practical, and researchers need to identify plant parameters responsible for the variation in methane emissions. Research must focus on rapid passage of digesta through the rumen of grazing animals and will involve manipulation of the fibre content of grasses. Introduction of CT into diets is a likely target to reduce methane production. Improving the rapidly digestible constituents of forages is another opportunity, but difficult to target. Keywords: condensed tannins, forage quality, forages, greenhouse gases, methane emissions, sheep
The objective of this study was to determine effect of pasture type on methane and carbon dioxide production by heifers grazing alfalfa or grass pastures at three sites across western Canada. All pastures were intensively managed so that heifers had ad libitum access to new forage material each day, and pastures were back-fenced to prevent the heifers accessing previously grazed areas. As measured using the sulfur hexafluoride (SF6) tracer technique, total methane production at the Brandon, MB, and Swift Current, SK, sites was unaffected by pasture type (averaging 157.4 g CH4 head -1 d-1), whereas at Lethbridge, AB, heifers grazing alfalfa produced more methane than did those on the grass pasture (162.8 vs. 113.5 g CH4 head-1 d-1; P < 0.05). Calculated with dry matter intake (DMI) estimated by alkane analysis, methane production per unit DMI was 39% lower from heifers consuming grass compared with alfalfa (P < 0.001). When intakes were estimated by the Cornell Net Carbohydrate and Protein System (CNCPS) model, CH4 production kg -1 DMI did not differ (P > 0.05) between pasture types. Loss of gross energy intake (GEI) to methane, as estimated by alkane analysis, was 6.9% for heifers grazing grass, and 9.6% for heifers grazing alfalfa (P < 0.001). Calculated using CNCPS, losses were similar (P > 0.05) between grass and alfalfa (5.8 vs. 6.2% of GEI, respectively). Carbon dioxide production per unit DMI did not differ between pasture types, irrespective of method used to estimate intake (alkanes or CNCPS). The method used to predict intake can have a major influence on calculated values when methane emissions are expressed as a percentage of GEI in grazing ruminants. At each site, CH4 emissions and in vitro digestibility of the forage were influenced by the composition of the stand and the maturity of the forage at the time of harvest.
In 3 experiments, the methane-suppressing effects of medium-chain fatty acids were investigated using basal diets of extensive type (high structural carbohydrate content) and intensive type (low structural carbohydrate content). In Expt 1, sheep were fed the extensive-type diet supplemented with 60 g/kg of rumen-protected fat (control) or coconut oil. The use of coconut oil in the diet did not clearly reduce methane release from the total digestive tract. In 2 in vitro experiments carried out with a RUSITEC apparatus, interactions of either coconut oil (Expt 2) or pure non-esterified lauric acid (Expt 3) with the 2 types of basal diet were determined using 2 × 2 factorial designs. Expt 2 confirmed a high efficacy of coconut oil against methane release in the intensive-type diet (suppression by 62% relative to control) and a reduced efficiency in the extensive-type diet (suppression by 6% relative to control). In contrast, pure lauric acid supplementation suppressed methane release in vitro by approximately 80%, and this was independent of the basal-diet type used. The results suggest that interactions of fat with the basal diet in the rumen have to be taken into consideration to develop effective feeding strategies against ruminal methane formation.