742
Pedreira et al.
RUMINAL METHANE EMISSION BY DAIRY
CATTLE IN SOUTHEAST BRAZIL
Márcio dos Santos Pedreira1; Odo Primavesi2; Magda Aparecida Lima3; Rosa Frighetto3;
Simone Gisele de Oliveira4*; Telma Teresinha Berchielli5
1
UESB - Depto. de Tecnologia Rural e Animal - 45700-000 - Itapetinga, BA - Brasil.
Embrapa Sudeste - 13560-970, São Carlos, SP - Brasil.
3
Embrapa Meio Ambiente - 13820-000, Jaguariúna, SP - Brasil.
4
UFPR - Depto. de Zootecnia, R. dos Funcionários, 1540 - 80035-050 - Curitiba, PR - Brasil.
5
UNESP/FCAV - Depto. de Zootecnia - 14884-900 - Jaboticabal, SP - Brasil.
*Corresponding author <sgoliveira@ufpr.br>
2
ABSTRACT: Ruminal gases, particularly methane, generated during the fermentative process in rumen,
represent a partial loss of feed energy and are also pointed to as an important factors in greenhouse
effect. This study aimed at quantifying methane (CH4) emission rates from lactating and dry cows and
heifers, 24 month-old in average, on pasture under Southeast Brazil tropical conditions, using the
tracer gas technique, sulphur hexafluoride (SF6), four animals per category, distributed in four blocks.
Measurements were performed in February and June, 2002, with Holstein and Brazilian Dairy Crossbred
(Holstein ¾ x Gir (Zebu) ¼), maintained on fertilized Tanzania-grass (Panicum maximum Jacq. cv.
Tanzania) and fertilized Brachiaria-grass (Brachiaria decumbens cv. Basilisk) pastures. Heifers of
both breeds were maintained on unfertilized Brachiaria-grass to simulate conditions of extensive
cattle farming systems. CH4 and SF6 levels were measured with gas chromatography. Differences in
CH4 emissions were measured (p < 0.05) for genetical groups. Holstein produced more methane (299.3
g day–1) than the Crossbred (264.2 g day–1). Lactating cows produced more methane (353.8 g day–1)
than dry cows (268.8 g day–1) and heifers (222.6 g day–1). Holstein, with greater milk production
potential, produced less CH4 (p < 0.05) per unit of dry matter intake (19.1 g kg–1) than the Crossbred
(22.0 g kg–1). Methane emission by heifers grazing fertilized pasture (intensive system) was 222.6 g
day–1, greater (p < 0.05) than that of heifers on unfertilized pasture (179.2 g day–1). Methane emission
varied as function of animal category and management intensity of production system.
Key words: feeding, genetical group, sulphur hexafluoride, tropical pastures
EMISSÃO DE METANO RUMINAL POR BOVINOS LEITEIROS
NO SUDESTE DO BRASIL
RESUMO: Gases gerados durante o processo de fermantação ruminal, metano em particular, representam
não só uma perda parcial de energia da alimentação como também são apontados como importantes
fatores do efeito-estufa. Quantificaram-se as taxas de emissão de metano (CH4) ruminal por vacas em
lactação, vacas secas e novilhas com idade média de 24 meses, em pastejo sob condições tropicais do
sudeste brasileiro, utilizando a técnica do gás traçador hexafluoreto de enxôfre (SF6). Foram utilizados
quatro animais para cada categoria, distribuídos em quatro blocos. As medições foram realizadas em
fevereiro e junho de 2002, com animais da raça Holandesa e Mestiça Leiteira Holandês ¾ x Gir ¼ Mestiças, mantidos em pastagem de capim-Tanzânia (Panicum maximum Jacq. cv. Tanzania) e capimbraquiária (Brachiaria decumbens cv. Basilisk) adubadas, e também novilhas de ambas as raças em
pastagens de capim-brachiaria sem adubação, simulando as condições de produção extensiva. As
concentrações de CH 4 e SF 6 foram determinadas por cromatografia gasosa. Foram encontradas
diferenças na emissão de metano (p < 0,05) entre os grupos genéticos. Animais da raça holandesa
produziram mais metano (299,3 g dia–1) que as mestiças (264,2 g dia–1). Vacas secas e novilhas produzem
menos metano (g dia–1) que vacas em lactação. A média de emissão de metano (g dia–1) pelas vacas
secas e novilhas foi de 268,8 e 222,6 g respectivamente e as vacas em lactação 353,8 g. Os animais da
raça holandesa, com maior potencial de produção de leite, perderam menos CH4 (p < 0,05) por unidade
de matéria seca ingerida (19,1 g kg –1) que as mestiças (22,0 g kg–1). A produção de metano pelas
novilhas mantidas em pastagens adubadas (sistema intensivo) foi de 222,6 g dia–1, maior (p < 0,05) que
os animais desta categoria em pastagens não adubadas (179,2 g dia–1). A produção de metano variou
em função da categoria de animal e pelo sistema de produção imposto aos animais.
Palavras-chave: manejo alimentar, grupo genético, hexafluoreto de enxofre, pastagem tropical
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
Ruminal methane emission by dairy cattle
INTRODUCTION
Ruminal gases yield are correlated to the microbial
activity in rumen, and methane, a gas generated during the fermentative process in rumen, represents a
partial loss of feed energy, with an accepted mean
value of 6.5% of the ingested gross energy (IPCC,
2006), varying from 2% by animals feeding on highgrain diets, to 12% when low quality forage is fed
(Johnson & Johnson, 1995; Johnson et al., 2007).
Methane (CH4) is also pointed as an important factor
on greenhouse effect, with enteric methane losses by
farmed ruminant accounting for about one fourth of
all anthropogenic emissions (Smith et al., 2007;
Lassey, 2008).
Methane production of grazing cattle can be affected by management practices and production level.
When the objective is weight gain, daily methane production by animal would be greater than in systems
targeting production per hectare. These differences
occur partially because of variation in forage availability
in both systems. Considering methane emission by
product unit (milk yield or weight gain per animal) values would be lower where gains per animal are greater,
but methane yield by surface area will be larger
(Kurihara et al., 1999).
Different methane amounts may be produced by
Bos indicus, Bos taurus and their breeds. These variations may be associated to the different characteristics of animals, like ruminal volume, feed selection capacity, retention time of feed in rumen, and associations of factors linked to lower or greater digestion
capacity of fibers in feed (Lassey et al., 2002).
Production phases may affect methane losses, linked
to dry matter intake. Considering that feed intake is a
function of body condition, pregnancy and lactating period (Mathison et al., 1995), distinct ruminal methane
amount were expected from each phase (Moss, 1994).
Abiotic factors that affect animal intake behavior as well
as forage quality may also be regarded. So, methane
production in different regions may differ, mainly between tropical and temperate climate environments.
Bovine ruminal methane emissions, under tropical
conditions, at the moment, were estimated, considering only feed characteristics and production potential
of animals. Considering that some environmental factors are related with these characteristics, real methane emissions may be different from these estimates,
as observed by Kurihara et al. (1999).
Studies quantifying methane and analyzing factors
that may reduce the production of this gas in tropical
environment, as an opportunity to improve the efficiency of energy utilization of feed, are timely. Thus,
this study aimed to quantify, the production of meth-
743
ane by ruminal dairy cattle kept on pasture in Brazilian tropical conditions of Southeast Brazil.
MATERIAL AND METHODS
Measurements were performed at São Carlos
(22º01' S, 47°53' W, 856 m altitude), SP, southeastern Brazil. The climate of the region is tropical with
wet summer and dry winter (Aw) or hot-dry winter
(Cwa) (Köppen, 1948), and original vegetation of the
Cerrado biome, with low fertility soils.
Trials were set up in in intensive system, with fertilized pastures plus concentrate diets. Experimental
design consisted of four randomized blocks, represented by consecutive weeks, main plots represented
by two breeds - Holstein and Holstein ¾ × Gir (Zebu)
¼ - Crossbred - and three categories: lactating cows,
dry cows and heifers; seasons represented subplots in
time, and treatments consisted of genetic groups: heifers, dry cows and dairy cows, one animal per treatment. Samples were taken twice a day (from 7 to 19
h from 19 to 7 h) for five days along four weeks each
season, in February (summer) and June (autumn). The
two daily measurements consisted of ten sub-samples
in the lieu of replications.
Mean live weight of animals tested, as well as mean
milk yield of lactating cows are presented in Table 1.
Lactating cows were in the third or fourth calving, and
the fourth or fifth week of lactation. Mean age of heifers were 24 months. Climatic characteristics of seasons appear in Table 2.
During summer, both lactating and dry Holstein
cows, and half of the Holstein and Crossbred heifers
were maintained on Tanzania-grass (Panicum maxicum
Jacq. cv. Tanzania) pasture, fertilized with 400 kg ha–1
of N and K2O each splitted five times after grazing,
with an initial liming to reach base saturation of 60%
and phosphorus to reach a content of 15 mg kg–1 soil,
after resin method, and under one day grazing pressure of 10.8 animal units (AU, 450 kg of live weight)
per hectare (ha) , and 35 days of resting time. Other
heifers were maintained on Brachiaria-grass
(Brachiaria decumbens cv. Basilisk) pasture, without
fertilizer and under a continuous grazing pressure of
1.5 AU ha–1 (extensive production system). The lactating Crossbred cows were maintained on fertilized
Brachiaria-grass pasture, under the same soil fertility
conditions of Tanzania grass pasture, with one day
grazing pressure of 10.8 AU ha–1, and 30 days of resting time for the forage. Pastures presented good forage availability, with uniform soil covering and height,
without occurrence of weeds. Extensively managed
pasture for heifers presented some weeds but maintained good soil covering with forage plants.
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
744
Pedreira et al.
Table 1 - Mean live weight and milk production of experimental units, with respective standard deviation.
Live we ight
Anima l c a te go r y
SD
M ilk p r o d uc tio n
SD
S umme r
Ho ls te in la c ta ting c o w
571.5
72
22.7
3.9
C r o s s b r e d la c ta ting c o w
478.5
86
13.3
2.1
Ho ls te in d r y c o w
605.0
18
-
C ro ssb re d d ry c o w
480.0
52
-
Ho ls te in he ife r 1
501.5
78
-
C r o s s b r e d he ife r
1
365.0
53
-
Ho ls te in he ife r 2
459.0
60
-
C r o s s b r e d he ife r 2
373.5
37
F a ll
Ho ls te in la c ta ting c o w
569.7
44
24.3
12.5
C r o s s b r e d la c ta ting c o w
474.2
52
9.7
2.4
Ho ls te in d r y c o w
641.7
15
-
C ro ssb re d d ry c o w
521.7
70
-
Ho ls te in he ife r
1
520.0
80
-
C r o s s b r e d he ife r 1
399.0
48
-
Ho ls te in he ife r 2
432.0
36
-
C r o s s b r e d he ife r 2
388.5
28
-
1
Intensive production system. 2Extensive production system. SD=Standard deviation, using four replications, represented by one
animal each.
Table 2 - Mean climatic characteristics during experimental seasons.
P e rio d
Ra in
mm
Te mp e ra ture
M a ximum
M inimum
Mean
Re la tive a ir Humid ity
Eva p o ra tio n (P ic hé )
%
mm
9.8
81
268
9.6
81
350
Amp litud e
- - - - - - - - - - - - - - - - - - - - - °C - - - - - - - - - - - - - - - - - - - - S umme r
Va lue
644
28.3
18.5
23.4
2002
677
28.1
18.5
23.3
F a ll
Va lue
142
25.4
14.2
19.8
11 . 2
74
321
2002
42
28.0
15.9
22.0
12.1
75
481
Note: Total values are considered for rain and evaporation; mean values for temperature and air humidity.
Holstein lactating cows received daily 1 kg concentrate per each 3 L milk, and Crossbred lactating cows
grazing fertilized Brachiaria pasture received 3.4 kg per
cow. Dry cows and heifers of both breeds maintained
on Tanzania-grass received 2 kg of concentrate per
animal. Heifers of both breeds grazing not fertilized
Brachiaria-grass pasture did not receive concentrate,
simulating the main Brazilian cattle raising conditions.
This experiment did not reach extreme negative structural pasture conditions (lower forage mass, highest
fiber and lowest crude protein). Intensive and extensive, were terms used to identify pasture fertilizer use
and use intensity for the category heifers. Lactating
cows of both breeds were used as comparison criterion for dairy production systems with greater or
lower technological level, not specifically to compare
breeds, since they were submitted to different diets as
the production capacity is not the same.
In fall, Holstein lactating cows were fed with corn
silage, 10 kg dry matter (DM) animal–1 day–1, and the
Crossbred with chopped grain millet, 8 kg DM animal–1 day–1, maintaining the same concentrate diet of
their specific herd, adjusted to production capacity and
daily requirements. Seasonal difference was the change
of feeding lactating cows from grass forage to silage.
The amount of concentrate remained the same as in
summer. Dry cows and heifers were fed as in summer.
Forage was sampled after McMeniman (1997), by
pooling 20 randomed 0.50 × 0.50 m-sub-samples cut
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
745
Ruminal methane emission by dairy cattle
to near soil surface, to estimate forage yield per hectare, and another sample simulating grazing, after following animals during grazing, avoiding disturbance of
grazing behavior, and identifying carefully consummated plant parts. More specifically by verifying plant
structure remaining at one site after grazing, and harvesting forage samples at a close site like at the grazed
site (McMeniman, 1997), to get similar forage chemical quality and digestibility. Also corn silage, grain millet
and concentrate were sampled for chemical analysis
(McMeniman (1997). After 48 h pre-drying in oven
at 60oC with forced air circulation, samples were
ground in a Wiley mill with a 1 mm sieve, and finally
dried during 8 h at 105oC. Pre-dried samples were
used to check DM content, crude protein (CP) after
the Dumas combustion method (Etheridge et al., 1998)
and neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin, with the sequential method described by Soest et al. (1991). For NDF evaluation was
used heat stable amylase and sodium sulphite. Lignin
content was calculated after analyzing the cellulose
content in sulphuric acid at 72% (Soest, 1994), considering the difference between weight loss of ADF
after analysis and the incinerated residue. Ash were
obtained by incinerating samples at 600oC, and organic
matter (OM) calculated (OM = 100 - ash). Organic
matter “in vitro” digestibility (OMIVD) was obtained
using Tilley & Terry (1963) method. Dry matter intake was estimated for each animal using NRC (2001)
dairy cattle model.
Forage yield, and feed quality and digestibility data
of both experimental periods are displayed in Tables 3
and 4. Prior to the ruminal air sampling, animals were
adapted during 15 d to the collection-store system
(holder and canister), to avoid stress influence on the
results, mainly related to DM intake.
The sulphur hexafluoride (SF6) tracer gas method,
described by Johnson et al. (1994, 2007) were used
to sample and quantify methane (CH4) emission. Permeation capsules with known SF6 emission rates were
prepared by gravimetry, measuring the mean weight
loss (considering four decimals) during four consecutive weeks and allowing a standard deviation of a maximum of 5%. Considerations of Lassey (2001) about
the capsules life length were regarded. Calibrated capsules were housed in the experimental animal’s rumen.
Used canister was a closed tube (0.002642 m3 volume)
prepared with a 60 mm outer diameter class 20 brown
PVC, pre-evacuated. The sampling system with a
0.0762 mm inner diameter capillary tubing, fixed on a
holder, was calibrated to fill the canister with around
half an atmosphere each sampling period (12 h). The
sampling system was connected to the canister with
a quick connect.
After animal adaptation to the collection and store
apparatus, the 2 × 12 h eructed ruminal gas was collected along five consecutive days, in two seasons. An
identical apparatus was placed on the fence to allow
the measurement of background CH4 levels in air. Since
background SF6 concentration at field level were under the limit of quantification (in the cases it was detected, concentration was around 2.3 to 3.2 ppt), they
were not considered, certainly different from experiments running in confinements.
Methane concentrations were measured with a gas
chromatograph HP6890, equipped with a flame ionization detector (FID) and megabore column (0.53 µm,
30 m) Plot HP-AI/M; and with an electron capture de-
Table 3 - Yield and quality characteristics of forage delivered to animals during experimental period.
Feed
FY
k g ha –1
DM
OM
CP
N DF
ADF
LI G
O M I VD
------------------------------------------- % --------------------------------------------S umme r
Ta nza nia 1
3,452
2
Ta nza nia
18.7
89.9
12.9
62.5
32.1
5.2
57.3
3,982
19.9
90.0
15.1
64.2
34.2
5.1
54.7
Bra c hia ria 3
3,734
30.6
91.1
7.2
68.6
34.6
7.2
48.0
Bra c hia ria 4
3,486
34.8
92.0
6.5
71.9
36.2
6.6
40.9
F a ll
C o rn s ila ge
-
34.6
96.2
7.5
47.9
25.6
4.9
57.5
C ho p e d M ille t
-
17.9
91.2
13.0
60.4
33.3
5.7
52.8
1,913
26.8
92.6
12.5
66.5
33.6
7.0
55.8
2,481
34.8
93.1
6.2
70.1
33.5
7.9
49.8
Ta nza nia 2
Bra c hia ria
4
FY = Forage yield; DM = Dry matter; OM = Organic matter; CP = Crude protein; NDF = Neutral detergent fiber; ADF = Acid detergent
fiber; LIG = Lignin; OMIVD = Organic matter “in vitro” digestibility. 1Tanzania grass, fertilized and grazed by Holstein lactating cows.
2
Tanzania grass, fertilized and grazed by both breed dry cows and heifers. 3Brachiaria grass, fertilized and grazed by Crossbred lactating
cows. 4Brachiaria grass, not fertilized and grazed by both breed heifers.
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
746
Pedreira et al.
Table 4 - Quality characteristics of concentrate delivered to animals during experimental period.
Feed
DM
OM
CP
N DF
ADF
LI G
O M I VD
---------------------------------------------------- % ---------------------------------------------------S umme r
1
86.3
94.1
27.1
23.3
14.5
1.5
75.2
C o nc e ntra te 2
94.6
94.5
21.6
27.9
15.3
1.4
64.7
3
94.5
94.5
21.6
27.9
15.3
1.5
70.7
C o nc e ntra te
C o nc e ntra te
F a ll
C o nc e ntr a te 1
89.0
94.9
25.4
33.6
9.3
0.8
73.9
C o nc e ntra te 2
90.4
95.4
21.8
31.1
8.8
0.9
68.3
3
90.4
95.5
20.8
32.3
9.4
0.9
64.7
C o nc e ntra te
DM = Dry matter; OM = Organic matter; CP = Crude protein; NDF = Neutral detergent fiber; ADF = Acid detergent fiber; LIG = Lignin;
OMIVD = Organic matter “in vitro” digestibility. 1Concentrate used for Holstein lactating cows. 2Concentrate used for Crossbred
lactating cows. 3Concentrate used for both bred dry cows and heifers.
tector (μ-ECD) with a megabore column HP-MolSiv
for SF6 measurement, with two 0.5 mL loop coupled
to six way valve, strictly as the method described by
Johnson et al. (1994, 2007). Columns were in parallel, each with its own sample loop. Elution time was
of around 1.6 min for CH4 and 1.67 min for SF6 each
replicate (three per sample).
After keeping away the canister from animals, they
were pressurized up to around 0.17 MPa (dilution of
content) with nitrogen 99.99%. Pressure before and
after dilution were read with a digital manometer. Calibration curves were obtained using certified standard
gases prepared by Praxair, containing 34 ± 9; 91 ± 9
and 978 ± 98 ppt SF 6, and 4,85 and 20 ppm CH4
(Westberg et al., 1998; Johnson et al., 2007).
For a batch of capsules used in present study, these
permeate typically 2.4 to 3.3 mg SF6 d–1. Ruminal
methane flux was calculated in relation to the SF6 flux
from capsules housed in the rumen, subtracting the
background CH4 level in air (Westberg et al., 1998):
QCH4 = QSF6 x ([CH4]y - [CH4]b)/[SF6]
where: QCH4 = ruminal methane emission rate; QSF6 =
known capsule SF6 emission rate; [CH4]y= canister
methane concentration; [CH4]b = background methane
concentration; [SF6] = concentration of SF6 in canister.
With the primary data, were calculated the CH4
emission per day and per kilogram of metabolic weight.
Mean values of ten emission readings per replicate of
each category were used since no great day-night emission differences were found. Also the CH4 emission per
dry matter intake and organic matter per digestibility
of dry matter and organic matter were calculated.
Analysis of variance was used to calculate the F
value, and Tukey test was used for significant treatments, with the ANOVA procedure from the SAS
(1999). To evaluate the significance of categories in
and between breeds the least square means were calculated, using the GLM procedure from the SAS.
RESULTS AND DISCUSSION
Methane production differed among breeds and categories, but no significant interaction occurred, either
between seasons or among interactions with breeds
and categories (Tables 5 and 6). When methane yield
was related to metabolic weight (g kg–0.75) no differences appeared between breeds, nor among the interactions.
When variables related to dry matter intake (DMI),
organic matter intake (OMI) and digestible organic
mater intake (DOMI) were analyzed, differences occurred between breeds and among categories, and their
interaction. For seasons only DMI presented differences for the interaction categories and season.
No differences were found between heifers of both
breed for methane production nor when related to the
metabolic weight, although differences occurred between pasture management system related to methane
losses, and also to methane production related to DMI
and OMI. Differences between seasons occurred also
for DOMI, but not when related to methane losses.
Methane emission was greater for Holstein compared to the Crossbred (Table 7), perhaps explained
by differences in animal body size, and more specifically by their organic matter intake potential, since there
is a direct relation between methane production and
digestible organic matter consumption, observed for
Holstein. Significant methane losses occurred among
categories, with lactating cows yielding more than dry
cows, and these more than heifers.
Results related to pasture management intensity (extensive and intensive) and concentrate use, with heifers of both breed, did not show differences between
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
747
Ruminal methane emission by dairy cattle
Table 5 - Variance analysis output for breed, animal category and season.
S o urc e s
S S o f De p e nd e nt va ria b le s
DF
DM I
O MI
DO M I
3 . 0 8 ns
36,997*
2.82*
C H4
g k g–1
DM I
1 7 9 . 8 ns
59.21**
14,817*
0 . 3 6 ns
96.9*
121.0*
11 0 . 1 9 *
45.84*
141,780*
1 7 3 . 6 ns
1 8 2 . 5 ns
5 1 5 . 3 ns
29.08*
25.25*
11 , 9 8 7 ns
0 . 5 6 ns
3 . 8 ns
6 . 2 ns
1 7 0 . 5 ns
50.58
23.74
48,358
5.04
–1
--------------- g d -------------Blo c k
3
0 . 7 6 ns
0 . 6 3 ns
Br e e d
1
142.59**
125.03**
C a te go ry
2
Br e × C a t
2
122.49*
30.26*
Er r o r ( a )
15
61.55
S easo n
1
0 . 1 9 ns
0 . 2 0 ns
0 . 6 6 ns
gd
–1
–0.75
g kg
10.03*
0 . 1 5 ns
7, 6 1 3 ns
1.69*
0 . 0 1 ns
0 . 0 9 ns
4, 5 9 6 ns
0.95*
11 . 0 5 ns
0 . 7 0 ns
1, 6 6 2 ns
0 . 11 ns
369.5
3 3 . 2 ns
g k g–1
O MI
2 0 5 . 1 ns
g k g–1
DO M I
381.6*
582.3*
427.1
1335.2
68.4*
225.0*
37.7*
3 8 . 0 ns
163.5*
5 1 . 7 ns
5 8 . 3 ns
Br e × S e a
1
C at × S ea
2
Er r o r ( b )
20
42.53
39.24
16.20
45,072
2.90
173.0
207.5
557.8
To ta l
47
415.49
10.6
366.48
312,883
24.46
1 , 11 9 . 2
1,314.2
3,982.8
11 . 0
174.26
12.1
13.8
12.7
7.4
C V (%)
Mean
14.92*
5 1 . 6 ns
16.9
14.3
14.3
14.5
13.7
281.7
2.7
20.6
22.3
38.5
Note: * = Significant at a level of 5% (*) or 1% (**); ns = not significant; SS = Sum of squares; DF = degrees of freedom; CV = coefficient
of variation. CH4 = Methane production; DMI = Dry matter intake; OMI = Organic matter intake; DOMI = Digestible organic matter
intake.
Table 6 - Variance analysis output for heifers in two systems of diet and pasture management, and season.
S o urc e s
S S o f De p e nd e nt va ria b le s
DF
DM I
O MI
DO M I
- - - - - - - - - - - - - - - g d –1 - - - - - - - - - - - - - Blo c k
3
12.09*
10.03*
Br e e d
1
3 1 . 11 *
26.12*
C a te go ry
2
2 . 1 3 ns
1 . 3 9 ns
g d –1
g k g–0.75
C H4
g k g–1
DM I
220.7*
g k g–1
O MI
262.3*
g k g–1
DO M I
5 1 4 . 6 ns
11 . 2 4 *
43,953*
3 . 11 *
7.06*
7 3 4 ns
15,061*
0 . 5 4 ns
4 0 . 2 ns
4 7 . 0 ns
1 7 2 . 4 ns
1 . 0 2 ns
77.9*
97.2*
1 , 2 3 1 ns
20,642
0 . 0 0 ns
1 9 8 . 9 ns
12.1
23.21*
Br e × C a t
2
2 . 3 6 ns
1 . 9 0 ns
0 . 8 5 ns
Er r o r ( a )
9
7.99
6.87
3.09
S easo n
1
0 . 6 2 ns
1 . 6 3 ns
2.19*
1 , 8 5 7 ns
0 . 3 9 ns
2 9 . 8 ns
4 8 . 2 ns
0 . 1 3 ns
1 3 . 2 ns
1 5 . 9 ns
1 4 . 2 ns
0 . 0 0 ns
0 . 4 ns
1 . 2 ns
2 1 8 . 2 ns
1.93
0 . 2 ns
128.5
0 . 2 ns
149.9
7 11 . 7
1 8 . 7 ns
Br e × S e a
1
1 . 3 9 ns
1 . 0 5 ns
0 . 3 6 ns
2 9 7 ns
S ys × S e a
2
0.82
1 . 0 9 ns
4 . 3 7 ns
2 6 3 ns
Er r o r ( b )
13
8.33
6.96
2.71
33,278
2.76
171.1
201.2
To ta l
31
66.85
57.04
55.07
11 7 , 3 1 6
9.91
681.8
823.1
988.3
2,849.0
7.0
6.9
25.2
21.6
20.7
20.7
22.8
200.9
2.1
8.5
11 . 4
200.9
2.1
17.5
19.0
38.3
C V (%)
Mean
Note: * = Significant at a level of 5%, ns = not significand, SS = Sum of squares, DF = Degrees of freedom, CV = Coefficient of variation.
CH4 = Methane production, DMI = Dry matter intake, OMI = Organic matter intake, DOMI = Digestible organic matter intake.
breeds, nor between seasons for the parameters related to methane production. Absence of differences
between seasons may have resulted from small variations in forage quality (Table 3), even when reduced
rainfall allowed lower forage availability in fall.
Data agree with those of Holter & Young (1992),
which pointed to differences in methane emission rates
between breeds and animal categories, as function of
differences in size of gastric compartments, and nu-
tritional requirements. The category lactating cow with
greater methane emission per animal, were also these
categories with greater DOMI, pointing to a relation
between these variables.
Taking into account characteristics of animals and
adopted management of the herd, with supplementation of diet in the dry season, a mean value for potential yearly methane production by lactating and dry
cows of 113.6 kg could be considered. This value is
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
748
Pedreira et al.
Table 7 - Methane production and feed intake as function of season, breed, category and management system.
Tr e a tme nt
C H4
g d –1
g k g–0.75 LW
LC
DC
Hint
He xt
403.2
280.0
222.2
198.4
3.45
2.30
2 . 11
1.99
LC
DC
Hint
He xt
332.6
294.5
232.6
181.0
3.57
2.90
2.75
2.12
LC
DC
Hint
He xt
383.2
261.3
245.0
157.2
3.28
2.04
2.25
1.65
LC
DC
Hint
He xt
296.3
238.4
190.6
180.3
2.92
2.21
2.12
2.05
Ho ls te in
C ro ssb re d
MS D
299.3 a
264.2 b
28.6
2.74
2.57
0.23
LC
DC
Hint
MS D
353.8 a
268.8 b
222.6 c
35.0
3.30 a
2.36 b
2.31 b
0.28
S umme r
F a ll
MS D
294.3
269.2
28.6
2.85 a
2.47 b
0.23
222.6 a
179.2 b
38.6
2.31 a
1.95 b
0.35
Hint
He xt
MS D
Ho ls te in
C ro ssb re d
ms d
205.7
196.1
38.7
2.26
2.00
0.35
S umme r
F a ll
MS D
208.5
193.3
38.6
2.24
2.02
0.35
DM I
O MI
DO M I
- - - - - - - - - - - - - - - - g d –1 - - - - - - - - - - - - - - - S umme r
Ho ls te in
19.19
17.48
10.87
14.99
13.58
7.89
12.78
11 . 6 0
6.81
12.21
11 . 2 4
5.61
C ro ssb re d
13.66
12.56
6.59
12.55
11 . 3 9
6.62
10.02
9.12
5.42
10.20
9.39
4.69
F a ll
Ho ls te in
17.64
16.86
10.64
15.42
14.36
8.10
13.13
12.23
6.90
11 . 5 9
10.79
4.04
C ro ssb re d
11 . 8 1
10.94
6.37
13.56
12.62
7.10
10.87
10.13
5.76
10.74
10.00
3.73
M e a n o f b r e e d , inte ns ive
15.52 a
14.4 a
8.53 a
12.08 b
11 . 1 b
6.31 b
0.88
0.84
0.54
M e a n o f c a te go r ie s , inte ns ive
15.57 a
14.46 a
8.61 a
14.13 b
12.99 b
7.43 b
11 . 7 0 c
10.77 c
6.22 c
1.08
1.03
0.66
M e a n o f s e a s o ns , inte ns ive
13.86
12.85
7.48
13.74
12.62
7.37
0.88
0.84
0.54
M e a n o f s ys te ms
11 . 7 0
10.77
6.22 a
11 . 1 8
10.35
4.52 b
0.61
0.56
0.35
M e a n o f b r e e d , in s ys te ms
12.43 a
11 . 4 6 a
5.84 a
10.46 b
9.66 b
4.90 b
0.61
0.56
0.35
M e a n o f s e a s o ns , in s ys te ms
11 . 5 8
10.79
5.63 a
11 . 3 0
10.34
5 . 11 b
0.61
0.56
0.35
C H4
DM I
O MI
DO M I
- - - - - - - - - - - - - g k g–1 - - - - - - - - - - - - -
21.0
18.8
17.4
16.1
23.1
20.7
19.2
17.5
37.4
35.7
32.9
36.1
22.0
16.9
18.7
13.5
23.0
18.1
20.1
14.5
36.6
32.2
35.3
39.5
24.4
23.8
22.9
17.6
26.5
26.2
25.2
19.2
51.0
44.7
42.4
38.7
25.6
17.8
17.4
16.7
27.6
19.1
18.6
18.0
47.4
33.8
32.6
48.8
19.1
22.0
1.8
20.7
23.9
1.9
35.0
42.0
3.2
23.2
19.3
19.1
2.2
25.0
21.0
20.8
2.4
43.1
36.6
35.8
3.9
23.4
19.7
1.8
23.5
21.1
1.9
40.7
36.3
3.2
19.1
16.0
2.8
20.8
17.3
3.0
35.8
40.8
6.7
16.4
18.7
2.8
17.8
20.2
3.0
36.0
40.6
6.7
18.5
16.6
2.8
20.3
17.8
3.0
37.5
39.0
6.7
Note: msd = Minimum significant difference with Tukey test. Lower case letters at the right side of numbers in column mean significant
difference among means. CH4 = Methane production, DMI = dry matter intake, OMI = organic matter intake, DOMI = digestible
organic matter intake. LC and DC = Lactating and dry cow, Hint or Hext = Heifers intensive or extensive.
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
Ruminal methane emission by dairy cattle
greater than that pointed by IPCC (2006) for grazing
lactating cows in Latin America, 63 kg year–1. These
differences occur as function of the estimates of feed
intake by animals, by animal breed, and variation in
methodology used to estimate methane emissions. Potential milk yield by reference animals of IPCC (2006)
inventory was of about 800 kg year–1, much lower
than the potential production of studied herd.
Methane production per unit of metabolic weight
was not different between breed, but differences occurred among categories, with greatest values for lactating cows, showing a greater nutrient intake related
to body weight. No differences occurred between dry
cows and heifers, although differences occurred in dry
matter and organic mater consumption, perhaps not
great enough to affect methane emissions by these categories. Differences occurred between seasons,
greater in summer, perhaps related to the characteristics of feed used in this season.
Parameter related to consumption of dry matter,
organic matter and digestible organic matter were different for breeds and categories, greater for Holstein
and lactating cows, because of the relation to animal
weight and type of diet. Analyzing DMI results for lactating cows, when keeping away concentrate intake,
point to estimated forage DMI of 2.4% live weight for
Holstein lactating cows.
These results related with forage quality, mainly
with the “in vitro” digestibility of organic matter, agree
with findings of Noller (1997), who suggested an expected daily dry matter intake of 2% and 2.5% live
weight by cows consuming forage with, respectively,
55% and 60% of TDN, with lower intake when forage availability is lower. For lactating Crossbred cows,
daily forage intake was estimated in 2.1% live weight,
probably overestimated since the forage OMIVD was
of about 50%, whose expected daily consumption
would be of around 1.7% live weight. These differences could be explained by possible differences in forage quality of sampled material and the forage really
consumed by animals, due to the selection capacity of
Crossbred cattle.
Holstein lactating cows consuming greater amounts
of digestible forage and concentrate, perhaps because
of their greater nutritional requirement, than Crossbred
lactating cows, produced more methane per day. A
greater intake of digestible organic matter will increase
CH4 emission per animal, but it will lead to greater production efficiency and therefore to a smaller methane
emission per product unit (milk or beef) or productive cycle (Moss, 2001). Comparing mean milk production (23.5 L d–1) and methane emission (393.2 g
d–1) by Holstein lactating cows with that of the Crossbred (11.5 L d–1 of milk and 314 g d–1 of CH4) it is
749
possible to calculate that CH4 production per liter of
milk is about 16.7 and 27.3 for Holstein and Crossbred, respectively, corroborating above statements.
Methane production, DMI, OMI and DOMI were
different between genetic groups, with greater CH4
emissions by the Crossbred, suggesting that Holstein
were more efficient to use organic matter of feed.
Variation in composition of diets, mainly forage quality and amount of concentrate, may contribute to these
differences, being not necessarily an effect of breed,
since organic matter of fiber will produce more methane than that of concentrates (Johnson & Johnson,
1995).
Among categories, lactating cows produced more
CH4 (g kg–1 of DMI, OMI and DOMI) than dry cows
and heifers. Methane production (as g kg–1 of DMI)
by lactating cows were 23.2 g, a little more than that
yielded by Cavanagh et al. (2008) in New Zealand (18.2
g), perhaps because of differences between diets and
animals, although this data (18.2 g) is 15.7% lower
than the reference value currently used in the New
Zealand national inventory.
Differences occurred regarding methane production per unit of organic matter and digestible organic
matter consumption between seasons, as a result of
variation in feed quality, mainly consummated forage,
although no differences for the amount of organic matter intake between seasons occurred, suggesting differences among animals. Considering the standard value
of energy released by each unit of feed dry matter as
18.451 MJ kg–1 (Ferrell, 1993) and the energy generated by methane as 0.05565 MJ g–1, it is possible to
estimate the energy loss as methane percent of ingested
crude energy (Ym) by Holstein lactating cows of about
6.4%, mean value suggested by IPCC (2006) for dairy
cows (6.5±1%) when poorer feed is available. Values
of Ym for Holstein and Crossbred animals were estimated to be about 5.8% and 6.6%, respectively.
Heifers from the intensive system produced meanly
222.6 g d–1 of methane, more than heifers from the
extensive system (179.2 g d–1 ), in accordance to
greater DOMI and also considering that diet in the intensive system were enriched by concentrate, leaving
to greater dry matter intake and methane emissions.
Pastures of the extensive system, with lower forage
quality and lower digestibility, suggest that daily methane yield per animal will be lower than in intensively
managed system, although animal production will be
jeopardized, leaving to longer production cycles, and
therefore to greater total methane emissions during animals’ productive life. Estimating the yearly potential of
methane production by the extensive system (65.4 kg)
it will be close to the IPCC (2006) reference for dairy
cattle raised on pasture in Latin America (63 kg).
Sci. Agric. (Piracicaba, Braz.), v.66, n.6, p.742-750, November/December 2009
750
Pedreira et al.
CONCLUSIONS
Intensive managed pasture systems, with fertilized
pasture and concentrate use, do generate more methane per day, but analysis need to consider the reduction of production cycle, with possibility of increased
animal productivity.
Variations in methane emission among genetic
groups, categories and production systems, point to
the need of more stratified studies to attend the inventory on methane emissions of the Brazilian bovine
cattle herd, due to distinct regional production characteristics in the country.
ACKNOWLEDGEMENTS
The research was funded by Financiadora de
Estudos e Projetos (FINEP). T.T. Berchielli is recipient of CNPq productivity fellowship; to Johnson, K
and Westberg, H. for technical support to the introduction of the SF6 method in Brazil.
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