© The Authors, 2023, Published by the Universidad del Zulia*Corresponding author: juanvergaralopez@gmail.com
Keywords:
Climatic change
Methane
Bovines Dual Purpose
Grazing
Supplementation
Ruminant grazing feeding and methane production
Alimentación de rumiantes a pastoreo y producción de metano
Alimentação de ruminantes em pastagens e produção de metano
Juan Vergara-López
University of Zulia, Faculty of Agronomy
Bolivarian Republic of Venezuela
Abstract
Climate change limits the release of radiation from the earth’s
atmosphere, a product of the accumulation of greenhouse gases (GHG) such
as CO
2
, methane, ammonia, among others. Ruminants contribute methane to
the atmosphere when fed with low quality forage diets, which in the light of
dierent conservationist organizations, qualies them as major pollutants.
When Venezuela signed the Kyoto Protocol in 2004, it undertook to establish
a GHG measurement system, as well as scientic research on the subject;
however, there are still no research groups in the country dedicated to the
permanent measurement of GHG contributions from these production
systems. Grazing pastures and forages of medium to low quality, with high
contents of cell wall of low degradability, produce a positive balance towards
the generation of methane of enteric origin, which could be mitigated if these
feeding schemes are improved, tending to improve the digestibility of basic
diets. Methane production by these production systems in the state of Zulia
is calculated at 209 Gg, 7.1 % of the total inventoried at the national level;
however, the lack of research in this area, as well as of systematic inventories
of local herds, prevents obtaining accurate data in this regard.
Rev. Fac. Agron. (LUZ). 2023, 40(Supplement): e2340Spl05
ISSN 2477-9407
DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v40.supl.05
Animal production
Associate editor: Dra. Rosa Razz
Agronomic
Engineer,
MSc. Animal
Production.
Professor.
Department
of
Animal
Science,
Faculty
of
Agronomy,
Universidad del Zulia, Maracaibo, Zulia, Venezuela.
Received: 02-10-2023
Accepted: 15-11-2023
Published: 11-12-2023
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ).
2023, 40 (Supplement): e2340Spl05. October-December. ISSN 2477-9407.
Resumen
El cambio climático limita la liberación de radiación de la
atmósfera terrestre, producto de acumulación de gases de efecto
invernadero (GEI) como el CO
2
, metano, amoniaco, entre otros.
Los rumiantes aportan metano a la atmósfera al ser alimentados
con dietas forrajeras de baja calidad, lo que a la luz de diferentes
organizaciones conservacionistas, les calica como grandes
contaminantes. Venezuela al suscribir el Protocolo de Kyoto en 2004
se compromete a establecer un sistema de medición de GEI, así
como investigación cientíca al respecto, sin embargo, actualmente
aún son inexistentes en el país los grupos de investigación dedicados
a la medición permanente de los aportes de GEI por parte de estos
sistemas de producción. La alimentación basada en pastos y forrajes
de mediana a baja calidad, con altos contenidos de pared celular de
baja degradabilidad, producen un balance positivo hacia la generación
de metano de origen entérico, lo que podría mitigarse si se mejoran
dichos esquemas alimenticios a n de mejorar la digestibilidad de
las dietas básicas. La producción de metano por estos sistemas de
producción en el estado Zulia, se calculan en 209 Gg, es decir, 7,1
% del total inventariado a nivel nacional, sin embargo, la carencia de
investigación en esta área, así como de inventarios sistemáticos de
rebaños locales, impide obtener datos certeros en este sentido.
Palabras clave: cambio climático, Metano, Bovinos Doble Propósito,
Pastoreo, Suplementación.
Resumo
A mudança climática limita a liberação de radiação da atmosfera
terrestre como resultado do acúmulo de gases de efeito estufa
(GEE), como CO
2
, metano, amônia, entre outros. Os ruminantes
contribuem com metano para a atmosfera ao serem alimentados
com dietas de forragem de baixa qualidade, o que, de acordo com
várias organizações de conservação, os qualica como grandes
poluentes. Quando a Venezuela assinou o Protocolo de Kyoto em
2004, comprometeu-se a estabelecer um sistema de medição de
GEE, bem como pesquisas cientícas a esse respeito. No entanto,
ainda não existem no país grupos de pesquisa dedicados à medição
permanente das contribuições de GEE desses sistemas de produção.
As pastagens e forragens de média a baixa qualidade, com alto teor de
parede celular e baixa degradabilidade, produzem um saldo positivo
na geração de metano de origem entérica, que poderia ser mitigado
se esses esquemas de alimentação fossem aprimorados por meio da
melhoria da digestibilidade das dietas básicas. A produção de metano
por esses sistemas de produção no estado de Zulia é estimada em
209 Gg, 7,1 % do total nacional. No entanto, a falta de pesquisas
nessa área, bem como a falta de inventários sistemáticos dos rebanhos
locais, nos impede de obter dados precisos a esse respeito.
Palavras-chave: mudanças climáticas, Metano, Gado de dupla
nalidade, Pastagem, Suplementação.
Introduction
Despite being one of the most important oil producers in the world,
Venezuela is a country that contributes a low level of Greenhouse Gas
(GHG) emissions, a similar situation in the case of methane of enteric
origin (MARNR, 2005). In 1994, Venezuela ratied the United Nations
Framework Convention on Climate Change (UNFCCC) and in 2004
acceded to the Kyoto Protocol through Ocial Gazette No. 38.081 of
December 7, 2004 (Venezuela, 2004, 2010). Venezuela’s adherence to
this convention imposes a series of commitments to be fullled, such
as the generation of inventories of GHG emissions by source and their
absorption by sinks, updated periodically; development of national
and/or regional programs to mitigate climate change and adapt to
the potential eects, strengthening scientic and technical research,
promoting the development of technologies, practices and processes
to control, reduce or prevent anthropogenic GHG emissions.
Reading the document of the First National Communication
on Climate Change in Venezuela (MARNR, 2005), the lack of
institutions and research groups actively registering GHG emissions
scientic data, especially in agricultural production systems, is clearly
documented. This leads the discussion to the non-existence of GHG
emission estimates in livestock production systems in Venezuela,
which places the country in a condition of non-compliance with the
commitments acquired with the adhesion to the convention.
On the other hand, ruminant feeding in these systems is based
on medium to low quality pasture and forage, which implies a high
contribution of methane to the atmosphere (Niggli et al., 2009; Vargas
et al., 2012). However, the supplementation options used by livestock
producers are usually commercial concentrate feeds or raw materials
with high contents of easily digestible carbohydrates, which favor the
digestion of the base diet and consequently, a decrease in emissions
(Hristov et al., 2013).
At present, the product of a political and economic crisis that has
driven the costs of goods and services to a state of hyperination,
as well as the foreign origin of raw materials for the formulation of
concentrated feed, an activity highly dependent on foreign currencies
controlled and limited by the state, are factors that have increased the
costs of these supplements. This situation has resulted in a decrease in
production levels in dual-purpose livestock, but also in an increase in
the generation of GHGs such as methane and, consequently, a decrease
in the eciency of dietary energy use (Waghorn and Hegarty, 2011;
Vargas et al., 2012).
Under a situation like the one described, it is necessary to
generate research oriented to the ecient use of pastures and forages
as basic feeds in the diet of ruminants, as well as the valuation of
supplementary raw materials whose detailed knowledge of chemical
composition, digestibility and biological quality in general, will allow
a rational use that complements the basic pasture and guarantees an
optimal rumen functioning, with minimum emission of GHGs such
as methane.
The objective of this review is to analyze the existing information
in the literature on ruminant feeding systems and, based on the
available regional herd data, to calculate the production of enteric
methane by these herds in order to determine if there really is a high
contribution of this gas to the pool of GHG produced in the country.
Methods
This review is referred to the calculation of methane production
by regional bovine herds, however, the inexistence of specialized
national literature on this aspect of digestive physiology in Venezuelan
institutions, lead to the use of literature originated in other latitudes,
where there is the capacity to carry out measurements of methane
production of enteric origin under dierent experimental conditions.
This bibliographic support allowed documenting the physiological
and metabolic processes that give rise to methane as a result of the
use of dierent dietary regimes; however, it is pointed out that such
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Vergara-López.
Rev. Fac. Agron. (LUZ). 2023, 40 (Supplement): e2340Spl05
3-7 |
Table 1. Representative livestock categories.
Main livestock
categories
Livestock subcategories
Mature milking cows
or bualoes
High-producing cows that have calved at least once
and are used primarily for milk production.
Low-producing cows that have calved at least once
and are used primarily for milk production.
Other mature cattle
or non-lactating
bualoes
Females
Cows used to produce calves for meat
Cows used for more than one productive purpose:
milk, meat, leather.
Males
Bulls used primarily for reproductive purposes
Steers used mainly for traction
Growing cattle or
bualoes
Preweaned calves
Replacement heifers
Growing cattle or bualoes/post-weaning calves
Connement cattle fed diets >90 % concentrates
Source: IPCC (2006, 2019).
The non-existence of national herd inventories available for
consultation prevents having ocial gures for their use in the
calculations pursued in this document; however, it was necessary
to use indirect sources, such as FAO’s FAOSTAT database (2023),
which has an inventory of the Venezuelan herd until the year 2021
of 16,221,020 cattle. On the other hand, the Venezuelan Minister of
People’s Power for Productive Agriculture and Lands, in October
of this year, referred on the social network Twitter that Venezuela
has 17,292,202 animals to date, of which 11,931,619 females and
5,360,583 males, while the state of Zulia has 18.60 % of the herd
and is the largest producer (Castro, 2023). The proportions referred
by Castro (2023), the only ocial source of this information, allow
calculating a herd of 3,216,350 animals for the state of Zulia. From
the ULA-CIAAL (2011) document, a proportion of cows of 35 %
can be extracted, which results in 1,125,723 cows and the rest of the
age categories in 2,090,627 animals, estimated inventories that were
used for the calculation of CH
4
of enteric origin incorporated into the
environment.
Discussion
Ruminant feeding
Ruminants have become one of the most important species from
the agri-food point of view, due to the production of milk and meat
that serve as a source of protein for the human diet, as well as other
benets, such as work and companionship. These animals feed on
plant species, predominantly grasses, which in turn serve as substrate
for the microorganisms that cohabit the rumen, predominantly
bacteria, fungi, protozoa and bacteriophages (Dearing et al., 2017;
Wang et al., 2017; Xia et al., 2020).
In the Venezuelan DPPS, crossbred Bos taurus × Bos indicus
animals are fed grazing as a basic diet (Urdaneta, 2009). Peña et
al. (1997) and Pariacote et al. (2012) report that in the Rosario and
Machiques de Perijá municipalities of Zulia state, this livestock
production system predominates, using Brahman, Holstein and Brown
Swiss breeds with dierent levels of crossbreeding and grazing on
grasses with high proportion of cell wall contents (Adesogan et al.,
2019).
information is generated under genetic, productive, climatic and
dietary conditions very dierent from Venezuelan conditions.
Literature was used preferably with a feeding management
based on grazing or by the inclusion of vegetable sources for animal
feeding, however, for the purpose of contrasting dierent dietary
schemes, articles that used some type of strategic supplementation
through concentrated feeds or raw materials were also considered. It is
important to point out that predominantly, research on this subject has
been carried out in countries with strengths in these measurements.
Thus, to document basic principles, classical literature (Church,
1988; Johnson and Johnson, 1995, Kurihara et al., 1999), necessary to
record the physiological basis of ruminant GIT, as well as the role of
the ruminal microbiota in the production of GHG (Hoover and Miller,
1991), was found. Similarly, opinions of environmental organizations
such as Greenpeace (2009, 2018) and journalists such as Lombardero
(2007) are documented, necessary to discuss the stigmatization and
defense of ruminants as GHG generators.
Regional Estimates of Enteric Methane Production
The Intergovernmental Panel on Climate Change (IPCC)
generates scientic information on the current state of climate change
and potential impacts on the environment and economy (IPCC, 2006,
2019; Smith et al., 2014). In the 1996 IPCC Guidelines and Good
Practice Guidance (IPCC, 1996), the simplest and most common
methodological approach to combine information on the extent
to which human activity takes place (called activity data or DA) is
performed with coecients that quantify emissions or removals per
unit of activity. These are called Emission Factors (EF). The basic
equation is therefore: Emissions = DA × EF.
IPCC methodologies use the concepts of good practices alluding
to the care of overestimates and uncertainties; “Tiers” referring to
levels of complexity, from the use of values reported in literature
to the use of models based on feed quality and productive states
of the herd; key categories to refer to the constituent age groups of
the regional herds; among other key concepts for the denition of
particular regional conditions. In a recently revised version, the IPCC
manual (2019) points out the use of Tier 2 or 3 methodologies, for
which it is necessary to have gross energy consumption (GEC) gures
and methane conversion factors for specic categories of livestock
or models based on the consumption of specic nutrients; however,
since there is no research of this type in Venezuela, this methodology
cannot be used.
On the other hand, in the methodology described in IPCC (2006),
it species that the main livestock categories and subcategories can
be classied according to the guidelines in Table 1, which are adapted
to the livestock categories used in dual purpose production systems
(DPPS) in the Maracaibo Lake basin.
For the purposes of this review, the Tier 1 methodology was used,
which consists of EF derived from the literature, which is multiplied
by the number of animals present in a country. These factors have also
been suggested by IPCC (2006) according to the type of animal and
geographical location, factors similar to those presented by Ungerfeld
et al. (2018), which correspond to 72 kg.head
-1
.year
-1
for dairy cows
and 56 kg.head
-1
.year
-1
for other types of animals (beef cattle, bulls,
calves, heifers). However, IPCC (2019) made changes for these FE,
for which it introduces the classication of high (3,400 kg milk.
head
-1
.year
-1
) and low production (1,250 kg milk.head
-1
.year
-1
) dairy
production systems, the latter classication in which Venezuelan
production systems fall. In this sense, IPCC (2019) species 78
kg.head
-1
.year
-1
for dairy cows and 58 kg.head
-1
.year
-1
for other types
of animals (beef cattle, bulls, calves, heifers).
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ).
2023, 40 (Supplement): e2340Spl05. October-December. ISSN 2477-9407.
These grasses are fermented by rumen microorganisms producing
volatile fatty acids (VFA) that feed the energy metabolism of these
animals, taking advantage of their capacity to degrade cellulose
(Church, 1988; Reyes Gutiérrez, 2012). Grazing of tropical grasses,
incorporating structural carbohydrates in dierent proportions,
produces more methane and promotes a higher acetic acid:propionic
acid ratio than fermentation of non-structural carbohydrates (Hyland
et al., 2016; Valencia-Salazar et al., 2022). In these diets, energy losses
to form methane are 8 to 12 % of the gross energy (GE) consumed
by the animal, but in the case of diets where commercial concentrates
(more than 90 % grain and high energy) are incorporated, methane
losses can be as low as 2 to 3 % of GE intake (Johnson and Johnson,
1995; Methol, 2005; Hyland et al., 2016).
Cattle production systems are the main producers of methane
among domestic ruminants, generating 7-9 times more methane
than sheep and goats. In cattle and other ruminants, approximately
80 % of methane is generated in the rumen, a product of cellulose
digestion by rumen microorganisms, while about 20 % comes
from the decomposition of fecal matter (Román and Hernández-
Medrano, 2016). At the rumen level, the conversion of CO
2
to CH
4
in microbial fermentative processes confers to the carbon product of
this conversion a Global Reheating Power (GRP) 21 times greater
than CO
2
(de Blas et al., 2008). As a result of these processes,
carbohydrates and proteins are cleaved to their simplest chemical
elements, such as monosaccharides and amino acids, which are
assimilated by microorganisms by specic metabolic pathways and
result in volatile fatty acids (VFA), CO
2
, CH
4
and heat (McDonald et
al., 1979; Vargas et al., 2012).
When analyzing the phenomenon physiologically, the production
of enteric methane in ruminants is carried out by pathways that
require important energetic inputs, which are provided by the diet.
There are several dietary factors that aect the digestion process
of raw materials in the ruminant GIT, among them the relationship
between the consumption of pasture, forage and concentrate feeds.
Animals with high contents of concentrates are subject to a decrease
in the pH of the rumen content due to a high digestibility of this
product and a decrease in the buering power of this medium due to
a dilution eect of the forage content. This decreases the populations
of cellulolytic ora to the benet of amylolytic ora, which decreases
ber digestion, leading to a decrease in acetic acid production and
an increase in propionic acid, which in turn leads to a decrease in
pH by release of protons (H
2
) increasing enteric methane production
(Oldham et al., 1977; Johnson and Johnson, 1995; de Blas et al.,
2008; Vargas et al., 2012).
Dietary factors and enteric methane emission in ruminants
The incorporation of highly digestible diets improves the use of
the energy contained in their carbohydrates, which translates into a
decrease in methane emissions. There are pasture species that are
more ecient in milk production, partly because of their low enteric
methane production due to a greater eciency in protein and energy
metabolism. Likewise, as the age of the plant increases, methane
production increases due to the eect of the increase in lignocellulosic
fractions (Carmona et al., 2005).
The non-utilization of energy due to methane gas production
is due to many factors: amount and type of feed, manipulation of
ruminal fermentation, addition of lipids, type of carbohydrate in the
diet and processing of forages (Carmona et al., 2005). These factors, if
controlled or manipulated, could become ecient alternatives for the
control of this type of emissions. Chandramoni et al. (2000) evaluated
dierent proportions of forage and concentrate feed incorporation
(F:C; 92:8, 50:50 and 30:70) in connement sheep, recording the
production of methane of enteric origin in relation to gross energy
and found that in the diet with a high proportion of forages (92:8),
methane production was higher (3.93 %) than in 50:50 and 30:70
(3.34 % and 2.98 %, respectively). The ndings of these researchers
led to the conclusion that less methane is produced in starch-rich diets
than in high-ber diets.
The inclusion of supplements high in easily digestible
carbohydrates promotes changes in the ruminal microora towards an
increase in amylolytic populations, which translates into a decrease
in the digestion of brous fractions, leading to a lower proportion of
acetate and a higher proportion of propionate (Oldham et al., 1977).
This metabolic scenario drives the rumen environment towards a
lower methane emission as described by Van Kessell and Russell
(1996).
In the Venezuelan DPPS, the use of commercial concentrate feeds,
alternative raw materials (produced or not within the production unit)
or agro-industrial by-products, traditionally constituted the elements
used as feed materials to make up for the deciencies inherent to the
medium to low quality of pastures and forages used as basic diet in
ruminants.
In a review by Ungerfeld et al. (2018), the processes by which,
carbohydrates during glycolysis and oxidative decarboxylation
of pyruvate to acetyl-CoA, reduce cofactors that are reoxidized to
continue ruminal fermentation are summarized; these cofactors
transfer electrons to protons forming H
2
, which is transferred from
the fermenting organisms to methanogenic Archaea, which use it to
reduce CO
2
to CH
4
(Carmona et al., 2005).
Methane, the main electron sink in the rumen, during propionate
formation also incorporates metabolic hydrogen from reduced
cofactors. Thus the production of acetate, and to a lesser extent
butyrate, from hexoses results in the release of reducing equivalents
that will be mostly available for methanogenesis, while propionate
production incorporates reducing equivalents competing with CH
4
formation (Bonilla-Sandí et al., 2020).
While it is true that there is a direct relationship between the level
of dry matter intake and CH
4
production (Hristov et al., 2013), it is
also true that the nutritional composition of the diet plays an important
role in CH
4
production. The presence of insoluble cell wall ber in the
diet favors a higher acetate:propionate ratio and, consequently, higher
CH
4
production. In contrast, fermentation of soluble carbohydrates
results in lower CH
4
production (Rivas-Martínez et al., 2023).
Estimation of methane production in ruminants
Advances in the understanding of ruminal fermentation have
allowed the development of mathematical models for the prediction
of enteric methane emission in ruminants. Hristov et al. (2013) and
Ungerfeld et al. (2018) have generated prediction equations with
dierent levels of complexity, estimating such emissions by relating
dierent productive stages, chemical composition of the diet, animal
products such as milk fat, or with animal behavior such as feed intake
or with live weight.
Johnson and Johnson (1995) in a detailed review of dierent
aspects related to CH
4
emissions in ruminants, state that when daily
feed intake (DFA) increases, the percentage of dietary GE lost as CH
4
(Y
m
) decreases on average 1.6 % per level of intake, however, the
linear mathematical model to predict this decrease fails and therefore
limits its extrapolation from laboratory to eld. When highly available
carbohydrates are fed at limited intakes, high fractional CH
4
losses
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This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Vergara-López.
Rev. Fac. Agron. (LUZ). 2023, 40 (Supplement): e2340Spl05
5-7 |
occur, while at high intakes of highly digestible diets, low fractional
CH
4
losses occur.
Yan et al. (2000) after a meta-analysis similar to the previous one
developed CH
4
prediction models based on digestible energy intake
(DEC) including silage acid detergent ber (ADF) (or DMI ratios)
and feed intake level. However, in the review by Hristov et al. (2013)
it is concluded that the validity of Y
m
is questionable, since according
to Ellis et al. (2010), this parameter does not have the ability to
dierentiate between a change in CH
4
produced due to an increase in
DMI and a change in CH
4
due to increases in dietary fat content, to
which they propose to express energy losses in CH
4
based on GE (or
per unit of animal product), which will more adequately reect forage
quality and other mitigation practices, such as the inclusion of grains
or fats in diets.
For growing, grazing-fed lambs, Hegarty et al. (2010) proposed
the following relationships between feed intake, digestibility (55 to
85 %) and CH
4
production:
• The increase in DMI is associated with a linear increase
in average daily weight gain (ADG), with the rate of ADG
higher in feeds of higher digestibility.
• The increase in DMI is associated with an increase in CH
4
production. In diets with low to moderate digestibility, such
as those in Australian extensive grazing systems, CH
4
release
per unit of additional intake is greater than when there is a
high intake of highly digestible feeds.
• CH
4
production per unit of metabolizable energy (ME) intake
is lower in diets with high energy densities.
• Although an increase in the intake of any diet reduces the
intensity of emissions in the growth phase (g CH
4
.kg
-1
LWG),
the intensity of emissions at any DMI level is lower in highly
digestible feeds than in low digestible feeds.
• Small changes in energy intake result in small changes in CH
4
production, but large changes in the productive performance
of the animal.
In the meta-analysis of Hristov et al. (2013) a total of 377
observations were analyzed, which allowed to ensure with an R
2
=
0.86 that DMI (specically digestible OM) is the most important
promoter of CH
4
production in ruminants, so that the dietary eect
and forage quality on intake is of utmost importance. The authors
clarify that, when using such an equation, the prediction error could
be higher with increases in DMI, since changing DMI to a narrower
range (ie. 10 % increase from approximately 18 to 20 kg.day
-1
) would
result in higher variability, making further research necessary to
nurture these predictions.
Dry matter intake and DE are the most important determinants
of milk and meat production, but the meta-analysis by Hristov et
al. (2013) did not include increased production or decreased enteric
CH
4
relative to production when increasing DMI. CH
4
increases with
increasing DMI, but if this phenomenon is viewed from a lens of
increased milk and meat production, CH
4
decrease would only be
achieved with increased feed eciency and genetically determined
productive potential in herds that would tend to be lower in high-tech
production systems.
Enteric methane contributions
Industrial processes and the burning of fossil fuels make a
signicant contribution of GHGs, which have been estimated
and discussed in the workshops of the IPCC, a body established
by the United Nations Environment Program (UNEP) and the
World Meteorological Organization (WMO) to generate scientic
information on the current state of climate change and possible
impacts on the environment and the economy (Smith et al., 2014).
According to the results of those workshops, agriculture contributes
about 14 % of GHGs, while, of these, methane occupies 18 %, and
animal agricultural production systems about 20 %, mostly due to
enteric fermentation (Smith et al., 2014). On the other hand, some
environmental conservationist organizations have pointed to cattle
as the main species responsible for this phenomenon. Greenpeace
(2009) in Brazil, points to the cattle-producing meat activity, not only
for the deforestation of 19,368 km
2
per year of the Brazilian Amazon
rainforest, but, consequently, for the increase of GHGs resulting from
this activity. The subsidiary of this same global organization in Spain,
ensures that, in this country, the livestock sector emitted in 2015 more
than 86 million tons of CO
2-eq
originated in the production of fodder
and grains for animal feed, followed by methane emissions produced
in the digestion of ruminants (Greenpeace, 2018).
In Venezuela, the extinct Ministry of Environment and Renewable
Natural Resources (MARNR), in inter-institutional workshops,
yielded gures of 2,950 Gg total CH
4
, while enteric fermentation
registers 757.2 Gg, i.e. 25.7 % of the total produced in the country.
For Zulia state, the national herd data referred to by Castro (2023)
and the EFs specied by IPCC (2006; 2019) and Ungerfeld et al.
(2018), allow calculating an estimated 209 Gg of CH
4
contributed by
this herd, which represents 7.1 % of the total CH
4
inventoried at the
national level and 27.6 % of the CH
4
of enteric origin reported in the
MARNR report (2005). Although these calculations place Venezuela
in very conservative conditions with respect to GHG emissions to the
atmosphere, it is also true that they should be taken with caution, since
the data were not produced under the conditions of the productive
systems, nor under Venezuelan agro-climatic conditions.
Conclusions
The feeding of grazing ruminants, based on the consumption of
high proportions of vegetable cell walls, generates a greater proportion
of methane of enteric origin in animal production systems.
The incorporation of supplements that improve the digestibility
of basic forage diets helps to reduce the generation of methane
of enteric origin in grazing ruminants, which also leads to a more
ecient productive performance, being able to achieve a shorter
stay of animals within the system, which translates into a lower
contribution of methane to the group of GHG that are incorporated
into the environment.
According to calculations made on the basis of data generated
by governmental institutions, the contribution of methane of enteric
origin was about 209 Gg, that is, 7.1 % of the total inventoried in
Venezuela, estimates that should be considered with caution, given
the foreign origin of the partial data used.
At present, Venezuela does not have scientic work teams with
the technological capabilities or research projects that contemplate
the permanent monitoring of GHG emissions produced in ruminant
production systems. However, there are laboratories in dierent
university or research institutions in the state, which have a
minimum installed capacity and the human talent to implement such
measurement systems.
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