1Laboratory of animal and food resources National Agronomic Institute of Tunisia
2Mateur Higher School of Agriculture of Mateur, Bizrte, Tunisia
3Ministery of Agriculture. CRDA Ben Arous, Tunisia
4Ministery of Agriculture, General Direction of Agricultural production, Tunisia
5Ministery of Agriculture, Pasture and Livestock Office, Mateur, Tunisia
Submission: November 05, 2018;Published: December 06, 2018
*Corresponding author: M’hamdi Naceur, Laboratory of animal and food resources National Agronomic Institute of Tunisia, Tunisia
How to cite this article: Takwa A, M’hamdi Naceur, Bouraoui R, M’hamdi H, Haykel H, et al. Environmental Impacts of Bovine Meat Production. Dairy and Vet Sci J. 2018; 8(4): 555742. DOI:10.19080/JDVS.2018.08.555742
Climate change threatening the well-being of current and future generations. Livestock sector plays an important role in climate change. Beef and cattle milk production account for most of the emission. The objective of this article was to provide an overview of the bovine meat production environmental impact. Especially, the main greenhouse gases (GHG) emitted by this subsector, the main GHG emissions sources and some mitigation strategies. Methane CH4 (the greenhouse gas related to animal emissions), Nitrous oxide N2O (the most powerful greenhouse gas) and Carbon dioxide CO2 are the main GHG emitted by beef cattle. The main emission sources considered include enteric fermentation, manure management, nitrogen inputs, direct energy, inputs used within the farm. Levers for mitigation strategies include animal feeding, productivity and flock management, nitrogen fertilization, management of rejections, energy reduction and carbon storage.
Now a days global warming is the most dangerous environmental problem that human can faces it. It represents a threat to the living being. Most people are still unaware of global warming and do not consider it to be a big problem in years to come. What most people do not understand is that global warming is currently happening, and we are already experiencing some of its withering effects. It is and will severely affect ecosystems and disturb ecological balance. However, 97% of climate scientists and researchers agree that humans have changed the Earth’s atmosphere in dramatic ways over the past two centuries, resulting in global warming .
The mainly cause of global warming is the continuous rise in planet’s temperature. And small changes in that temperature correspond to enormous changes in the environment [1,2] affirm that this rise in planet’s temperature causes by increasing of greenhouse gases rate in atmosphere such as carbon dioxide CO2, methane CH4 and nitrous oxide NO2. Therefore more, Steinfeld et al (2006) state that three of the most important greenhouse gases; carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), are emitted largely due to livestock activities. Also, according to the FAO report livestock production contributes to 18% of total anthropogenic greenhouse gases emissions.
In the other hand, in European Union livestock sector is major of agricultural economy and its land use. There is
a different subsector and within each subsector a range of different production systems, we note a rise of intensification, larger farm units and more diversity of farming systems . Andrien  note that according to the CAPRI model calculations agriculture sector emit 49% of total GHG emissions, 21% from energy sector, 2% from industrial sector and 29% from land use and land use change. About the livestock sector, European livestock production emit a total GHG fluxes of 661 Mio tons of CO2-eq, which is distributed as follows: 29% are coming from beef production, 29% from cow milk production, 25% from pork production, 17% are coming from all other animal products.
Therefor more, Pelletier et Tyedmers report that by conjunction, in 2050 direct GHG emissions from meat, milk and egg production are projected to increase by 39% over the year 2000. So, meat beef production one of the major sub-sectors of livestock sector that contributes to GHG emissions. We focus in this study on beef production GHG emissions and mitigation strategy applied to mitigate this environmental impact.
According to Steinfeld  because of the increase of the population and the rise of the standard of living between 2000 and 2050 the demand of meat will split of 229 million tons per year to 465 million tons per year. According to Table 1 the largest
quantity of beef is produced by the USA in 2012. In the other hand
beef cattle is one of the most species which emit GHG (Figure 1).
The greenhouse gases comprise only about 1% of the total
gases in the earth’s atmosphere. The predominant gases are
oxygen (21% of the total) and nitrogen (78% of the total).
The primary greenhouse gases are carbon dioxide, methane,
nitrous oxide, ozone and water vapor. These gases trap infrared
energy that contributes to higher atmospheric temperatures.
It is important to remember that carbon dioxide, methane and
nitrous oxide are continuously emitted and removed from the
atmosphere by natural processes. In addition to these natural
processes, anthropogenic activities also cause emissions of some
of these gases .
There are mainly CO2, CH4 and NO2. But there are also other
gases such as fluorinated gases (CFC, HFC, PFC, SF6) that do not
concern the agricultural field. Each gas is characterized by their
global warming potential, it is the cumulative heating forcing
over a defined period. It is measured in relation to CO2 and is
expressed in kg CO2 equivalent . The main gases emitted by
beef cattle are: Methane CH4, Nitrous oxide N2O and Carbon
dioxide CO2. As an example, Figure 2 shows an overview of
greenhouse gases and sources of greenhouses gas emissions in
US in 2013. This figure is from the Environmental Protection
Agency website characterizes US greenhouse gas production.
According to Figure 2: Methane represents 9%, Nitrous oxide
represents 2% and Carbon dioxide represents 84% of total US
greenhouse gases. While, agriculture is responsible for 8% of the
total US greenhouse gas emissions.
Methane is the greenhouse gas related to animal emissions
. Their warming potential is 25 kg CO2/Kg of CH4. The plant
diet of cows and other ruminants is high in cellulose, which
cannot be digested by the ruminant itself. However, ruminants
have a symbiotic relationship with colonies of microorganisms,
called methanogens, which live in their gut and break down
the cellulose into carbohydrates. These carbohydrates provide
both the microbial community and the ruminant with an energy
source. Methane is produced as a by-product of this process.
Machen & Mccollum  says that methane is a loss of dietary
energy during digestion by microorganisms in the rumen.
Nitrous oxide warming potential: 298 kg CO2/kg of NO2.
Nitrous oxide is a very sensitive greenhouse, it has a 296
times higher impact than CO2. One of important sources of N2O
emissions is agricultural activities such as: The use of nitrate
fertilizers, livestock production, and manure management.
N2O is generated as an intermediate product or by-product of
nitrification and denitrification processes. Their emission is
very complex . NO2 issues from nitrogen fertilizers (organic
manures or inorganic fertilizers) or by manure storages and by
deposition by grazing animals [9,10]. 50% of NO2 emissions is
form animal agriculture . The nitrogen excreted more in
the urine whereas the nitrogen excreted in the dung is constant
Carbone dioxide CO2 has a lower warming potential then
CH4 and NO2, but it has the most emitted gas especially from
industrial sector. The use of fossil fuel is the most important
emissions source of CO2, it can be also emitted by from land use,
degradation of soil .
Dollé  have defined 5 mainly sources of emissions:
a. Enteric fermentation: CH4 emissions from animal
biological activity of cattle: Enteric fermentation is a process
that characterizes ruminants. It occurs at the rumen level. It
produces methane as a byproduct of a microbial fermentation
of carbohydrates into simple molecules .
b. Manure management: CH4 and NO2 emission from the
management of rejections (pasture, building, storage).
c. Manure contains two chemicals components: Organic
matter converted to CH4 by anaerobic decomposition, mostly
when manure is managed in liquid form, Nitrogen leads
to nitrous oxide emissions by indirect transformation of
nitrogen released in the atmosphere to ammonia NH3 and
then to N2O.
d. Nitrogen inputs: NO2 emission resulting from the
nitrification and denitrification phenomena of direct
nitrogen inputs through organic and mineral fertilization and
indirect nitrogen inputs by nitrate leaching and ammonia
e. Direct energy: CO2 emission from fossil fuels consumed
on the farm (electricity and fuel).
f. Inputs: CO2 emission from transport of cattle feed, NO2
emission from fertilizer manufacturing.
Therefore more, Andrian cited different emissions sources of
beef which are illustrated in Table 2: Andrian considered CH4
from enteric fermentation is the important GHG source. While
Gerber his model GLEAM (Global Livestock Environmental
Assessment) ranked the sources of GHG emissions as shown in
a. The greenhouse gases emissions variation factors
b. Rumen activity and Animal feed
c. Rumen activity
The rumen is home to millions of microorganisms that
digest food into co-products. Methane production in the rumen
is related to the size of the protozoa. If the size of protozoa
increases methane production also increases. It is also related to
the percentage of hydrogen used to make methane .
Fibrous and poorly digestible diets cause an increase in
CH4. In the other hand According to Machen et Mccollum diet
influences the amount of methane. Cattle that consuming
stem forage (high fiber) emit more methane then cattle that
consuming concentrate (low fiber). They add that when highly
available carbohydrates are fed at limited intakes, high fractional
methane losses occur. At high intakes of highly digestible diets,
low fractional methane losses occur.
There is a relationship between productivity and GHG
emissions intensity, when productivity and yields increase
GHG emissions intensity decreases. According to Gerber poorer
animal husbandry, lower slaughter weights and higher age
at slaughter leading to higher GHG emissions. An increase in
productivity without an excessive reliance on inputs that allows
for an increase in the average daily gain, this leads to a reduction
in the fattening time, and consequently a reduction in GHGs
emissions associated with production. Guickshank assert that
a good herd management: an adequate diet, a good reform of
unproductive animals, an effective health management capacity
to adapt to environmental changes, leads to a reduction of 2 to
5% of GHGs emitted by cattle farming.
Soil change is reflected in a change of carbon flux in the
soil, it is carbon storage and restorage. This can lead to GHG
emissions of carbon sequestration. Any conversion of a forest or
grassland into a crop induces GHG emissions (from 4 to 6 tonnes
of CO2 / ha / year). Conversely, any conversion from a crop to a
grassland induces sequestration of carbon in soils (from 0.84 to
2.75 tonnes CO2 / ha / year) . According to Table, soil change
from crop to grassland is better than soil change from grassland
to crop because it mitigates CO2 emission and capture CO2
Proper nitrogen management can reduce 90% of CO2
emissions . Much of the nitrogen management is evident in
the management of N input at the farm level. Moderate nitrogen
fertilization reduces the purchases of synthesized fertilizers
and consequently reduces carbonic gases emissions associated
with their manufacture and transport (5.3 to 6.1 kg of CO2/kg of
Energy consumption within a farm is the major factor for
CO2 emission. Dollé assert that the consumption of fuel and
electricity causes the direct emission of CO2. So, any reduction in energy consumption will reduce the CO2 emission (mitigation
strategies of energy consumption are more detailed in the third
Technologies and practices that help reduce emissions exist
but are not widely used. Their adoption and use by the bulk of
the world’s producers can result in significant reductions in
emissions. Dollé summarize action levers that can reduce GHG
emissions from cattle (Table 4) it’s through means that act on
Animal feed, productivity and herd management, nitrogen
fertilization and manure management, reduction of energy
consumption and carbon storage. Table 5 shows this means and
their effect on CH4, NO2 and CO2 emissions.
Focusing on animal feed (Table 4), we can use additives
to limit enteric fermentation . Or changing animal diet for
example changing grass to maize can reduce methane from
enteric fermentation . Also, increase the part of concentrate
in the ration, which replaces cellulose by starch, so it can reduce
enteric methane. To reduce the production of methane in the
rumen we can decrease the population of the protozoa by the
ingestion of rations very rich in cereals. Or redirect the hydrogen
used in the manufacture of methane in other biochemical
pathways such as the sulphate or nitrate reductant route.
Similarly, polyunsaturated fatty acids represent hydrogen sinks
(capture hydrogen) so they try to reduce methagenesis.
Concerning mitigation strategy applied to reduce methane
and other GHG emissions from manure management we can site:
a. Composting, by aerating and ventilating stored manure,
this decrease CH4 emission but increase NO2 emission from
b. Excessive use of straw in litter can reduce GHG emission from manure .
c. -Manure compacting and coverage by plastic sheeting
reduce CH4 but may increase NO2 according to climatological
In the other hand, according to Weske  more lactations
per cow, less enteric methane emission. Because without
producing milk there is more GHG emissions.
As example of mitigation strategy of NO2 emissions from
agriculture soil is nitrification inhibitors which can reduce
roughly 30% of NO2 emission from soil . Nitrification
inhibitors can reduce losses by leaching and consequently
reduce emissions, by slowing the production of nitrate nitrogen
resulting from the transformation of the ammoniacal nitrogen of
pissats and manure. This reduction can reach 60 to 68% of GHG
emissions. This strategy is very much studied in New Zealand
. According to Soussana  reducing grazing intensity or
overgrazing, reduce both NO2 emissions and soil organic carbon.
In the other hand, the division of ploughing grassland in
several times per year instead of ploughing permanent grassland
can reduce NO2 emissions from the soil. Or reducing ploughing
area by leaving areas un-ploughed and sowing new seed under a
no-till system . According to Wulf  most effective way to
reduce NO2 and CH4 both emissions from manure management
is trail hose application in combination with immediate shallow,
but that can increase NH3 emissions. Therefore more, the use
of cropped crops, such as energy crops as buffer strips along
open streams in order to mitigate nutrient leaching, so reducing
NO2 in the atmosphere [30-32]. Focusing on manure biosolid
management strategies such a: compacting and coverage,
increasing straw content for composting, covering manure
storage, no manure application in autuum, mitigates both NO2
and CH4 emissions gases. Also, the use of legumes reduces NO2
emissions, thanks to symbiotic fixation that dos nit emits GHGs.
There are two main levels of CO2 mitigation strategies:
a. Carbon storage
Extensification can reduce CO2 emissions from soil by turning
grassland into a carbon sink instead of a source. So, increase the
proportion of permanent grassland. Implementation of hedges.
Practice grazing instead of the installation of cultures has
end of underestimate the consumption of fuel for harvesting,
distribution of forage, spreading of droppings, reduce CO2
emissions from fuel use [33-35]. On the other hand, checking the
tractors, good economic driving, reducing transport, simplifying
farming practices…, can significantly reduce CO2 emission from
energy use .
Methane CH4, Nitrous oxide NO2 and Carbone dioxide
CO2 are the main GHGs emitted by beef cattle. NO2 is the most
powerful GHG, which retains more heat than CH4 and CO2.
Enteric fermentation, manure management, energy use and
nitrogen inputs are the main GES emissions sources from bovine
meat sector. Cattle is the agriculture sector that emits the most
GHGs. So the aim is not only to encourage and support research
and GHG abatement strategies, but also to popularize and raise
awareness among all members of agricultural sector, especially
producers, in order to highlight the seriousness of this situation,
to find viable and achievable solutions.
More communication with farmers is needed, new policies
and investments that facilitate the use of mitigation solutions.
Meat production increases as demand increases. Therefore,
adequate strategies are needed to limit GHG emissions while
guaranteeing food safety, the state of the animal and avoiding any
undesirable effects. We must strive for sustainable agriculture
that preserves our natural and environmental resources.