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Prediction of methane energy output in dairy and beef cattle
offered grass silage-based diets
1 1
*
T. Yan , R.E. Agnew , F.J. Gordon , M.G. Porter
The Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down, Northern Ireland BT26 6DR, UK
Received 9 November 1998; received in revised form 2 August 1999; accepted 11 August 1999
Abstract
Since 1992 a number of lactating dairy cows (n5247) and beef steers (n575) were offered grass silage-based diets in a range of feeding experiments and subjected to gaseous exchange measurements in calorimetric chambers at the Agricultural Research Institute of Northern Ireland. The objective of the present study was therefore to use the energy metabolism data from these studies to evaluate the relationship between methane energy output (CH -E) and a number of animal and dietary4
factors. There were no significant differences between dairy and beef cattle in terms of silage dry matter (DM) intake as a proportion of total DM intake (SDMI/ TDMI), total acid detergent fibre (ADF) intake as a proportion of TDMI(TADFI/ TDMI) or silage ADF intake as a proportion of TADFI (SADFI/ TADFI). Animal type also had no significant effect on CH -E as a4 proportion of gross energy (GE) intake (CH -E / GEI) or digestible energy (DE) intake (CH -E / DEI). The data from both4 4
dairy and beef cattle were thus pooled to predict CH -E. CH -E / GEI and CH -E / DEI were each significantly related to4 4 4 feeding level or dietary factors (P,0.001). These two ratios (CH -E / GEI and CH -E / DEI) were reduced by pro-4 4
portionately 0.0078 and 0.0123, respectively, as feed intake increased one level above maintenance. However an increase of 0.10 in SDMI/ TDMI, TADFI/ TDMI or SADFI/ TADFIwould increase CH -E / GEI by 0.0025, 0.0069 or 0.0048; or CH -E / DEI4 4
by 0.0035, 0.0107 or 0.0067. CH -E (MJ / day) was significantly related to GE or DE intake (P4 ,0.001) with a coefficient of 0.055 or 0.071 and a constant of 3.23 or 3.32. The prediction of CH -E was thus examined using various combinations of4
intake (GE or DE) with feeding level above maintenance or / and dietary factor (SDMI/ TDMI, TADFI/ TDMI or SADFI/ TADFI).
2
The relationships were all highly significant (P,0.001) and the R values ranged from 0.851 to 0.888. The equations
2
relating CH -E to DE intake, feeding level above maintenance (FL-1) and S4 ADFI/ TADFI or SDMI/ TDMI had the highest R value, and these two equations also gave the most accurate prediction when using published results. These two equations are
CH -E (MJ / day)4 5DEI (MJ / day) (0.09410.028 SADFI/ TADFI)22.453 (FL-1)
CH -E (MJ / day)4 5DEI (MJ / day) (0.09610.035 SDMI/ TDMI)22.298 (FL-1) 2000 Elsevier Science B.V. All rights reserved.
Keywords: Cattle; Grass silage; Methane prediction; Energy intake; Feeding level
*Corresponding author.
E-mail address: [email protected] (T. Yan) 1
Also members of staff of the Department of Agriculture for Northern Ireland and The Queen’s University of Belfast.
1. Introduction major differences due to level of intake. Over the last 2 decades cow genetic merit has substantially in-creased (Coffey, 1992) and these animals can The metabolisable energy (ME) concentration in
produce milk yields of over 50 kg / day and consume the diet of ruminant animals is determined as the
more than 300 MJ / day of ME (Yan et al. 1997a), a difference between gross energy (GE) intake and
level which can be over five times their maintenance energy outputs in faeces, urine and methane. The
requirement as estimated from the Agricultural and measurement of methane energy output (CH -E)4
Food Research Council (1990). Beever et al. (1998) requires complex and expensive equipment and
0.75 hence prediction equations are widely used to calcu- also reported a mean ME intake of 1.89 MJ / kg late CH -E. A number of these equations have been4 with lactating cows, which is approximately four published since 1930, using total dry matter (DM) levels of feeding calculated from the Agricultural intake (Kriss, 1930; Axelsson, 1949), digestible and Food Research Council (1990). The effect of carbohydrates (Bratzler and Forbes, 1940; Moe and feeding level on methane production is therefore Tyrrell, 1979), energy digestibility and feeding level becoming of increasing importance and there is (Blaxter and Clapperton, 1965), and a range of therefore a need to re-examine this effect.
animal and dietary factors (Holter and Young, 1992). At this Institute, between 1992 and 1997 a number However, the data used to develop these equations of experiments have been completed with lactating were collected from ruminant animals offered diets dairy cows (n5247) and beef steers (n575) offered containing mainly dry or high DM forages, rather grass silage-based diets and subjected to gaseous than low DM grass silages, typical of those used in exchange measurements in calorimetric chambers. many areas of Western Europe. The fermentation The objective of the present study was therefore to process in low DM grass silage results in a low use the energy metabolism data from these studies to concentration of water soluble carbohydrates and evaluate the relationship between methane product-high levels of fermentation products, such as volatile ion and a number of animal and dietary factors. fatty acids (VFAs), lactate, alcohol and ammonia.
Furthermore, the concentration of fibre in the DM of
silage can also differ from that in dried grass due to 2. Material and methods the ensiling process and differences in harvesting
date. The feeding of grass silage can therefore result 2.1. Animals and calorimeters in different fermentation patterns in the rumen when
metabolism unit, each animal was subjected to a Thirty-five dairy cows and twelve beef steers (each 6-day diet balance measurement with total faeces and from a single experiment) were offered silage as the urine outputs being collected. Immediately after sole diet, but otherwise in all other experiments the completion of the balance measurement, each animal dairy and beef cattle (n5275) were offered the was transferred to respiration calorimeters. The silages with a range of proportions of concentrates animals remained in the calorimeters for 3 days with from 0.146 to 0.815 (DM basis) with a mean of measurement of gaseous exchange over the final 0.467 (S.D. 0.1484). The concentrates used in each 48-h period. The dairy cows were of various genetic of the studies included a mineral / vitamin supplement merits and at a range of lactation stages (milk yield and some of the following ingredients,
from 3.2 to 49.1 kg / day with mean of 23.2 (S.D.
8.07) kg / day). The lactation number for the dairy Cereal grains: Barley, wheat or maize
cows ranged from 1 to 9 and liveweight from 416 to By-products: Maize gluten meal, molassed sugar-beet 733 (mean 565, S.D. 23.6) kg. The age and pulp, citrus pulp or molasses
liveweight of the beef cattle ranged, respectively Protein supplements: Fish meal or soya-bean meal from 18 to 21 months and from 450 to 644 (mean
531, S.D. 31.1) kg. The concentrate portion of the diet was offered The calorimeters used in the present study were either in a complete diet mixed with the grass silage, indirect open-circuit respiration calorimeters. All or as a separate feed from the silage. All animals equipment, procedures, analytical methods and were offered either silage or the complete diet ad calculations used in the calorimetric experiments libitum. The data on mean, S.D. and range for were as reported by Gordon et al. (1995b). Cali- animal, silage composition, total diet and energy bration of the chambers is carried out in two stages, utilisation variables are presented in Table 1. As the i.e. analyser calibration and flow calibration. Firstly, data set is combined from both lactating dairy cows the analysers are calibrated with gases produced and beef steers, there was a wide range in live from individual pure analytical standard gases weight, DM intake, feeding level, methane energy (methane, carbon dioxide and oxygen) using Wostoff output and energy intake.
Mixing pumps. This determines the absolute range Gross energy (GE) concentration in silages was (0–500 ppm for methane) and the linearity within determined using undried silages in an adiabatic this range. Before each run the analysers are cali- bomb calorimeter (Gallenkamp, Loughborough, UK) brated using oxygen free nitrogen and a gas of (Porter, 1992). Silage DM concentration was de-known concentration (span gas). This calibration is termined on an alcohol–toluene basis, which was checked automatically every 6 h. Secondly, the flow subsequently used as a basis of expressing all measurement systems are checked with analytical nutrient concentrations in silages. Analysis for other grade carbon dioxide and nitrogen using, respective- nutrients in feeds, faeces and urine were as described ly the carbon dioxide and oxygen analysers, by by Gordon et al. (1995b) and Mayne and Gordon determining the recovery of carbon dioxide and (1984).
depletion of oxygen.
2.3. Data analysis 2.2. Diets
Table 1
Data on animal, diet and energy metabolism for both dairy and beef cattle
Mean S.D. Minimum Maximum
Acid detergent fibre (g / kg DM) 375 53.9 301 486
Total diet (n5322)
DM intake (kg / day) 14.61 4.939 5.55 24.26
Silage DM / total DM intake 0.544 0.2334 0.169 1.000
Total ADF / total DM intake 0.248 0.0615 0.137 0.372
Silage ADF / total ADF 0.782 0.1538 0.409 1.000
Feeding level 3.23 1.061 1.28 5.71
(Agricultural and Food Research Council, 1990)
Energy utilisation (MJ / day) (n5322)
Gross energy intake 271.9 92.34 105.5 454.6 (GE or DE) and FL above maintenance (FL-1) or
1d (FL-1) (IV)
dietary factor (TADFI/ TDMI, SDMI/ TDMI or SADFI/ TADFI) (Eqs. IIIa–b). Finally, CH -E was predicted4
The above equations were fitted, respectively to using the above three groups of variables, i.e. energy
the following three equations intake (GE or DE), feeding level (FL-1) and dietary
factor (TADFI/ TDMI, SDMI/ TDMI or SADFI/ TADFI) y5ai1b1?x1
(Eq. (IV)) y5a 1b1?x11b2?x2 i
y5ai1b1?x11b2?x21b3?x3
CH -E4 5a1b?intake (I)
where a represents the effect of experiment i fori i51 to 13, x1, x2, and x3 are the x-variables and b1, CH -E / intake4 5a1b?digestibility (IIa)
b2 and b3 are their regression coefficients. The
feeding level (FL) is estimated as multiples of ME CH -E / intake4 5a1b?[FL-1] (IIb) intake (MEI) over ME requirement for maintenance
Research Council (1990). The statistical programme ing from 0.639 to 0.847) had no significant relation-used wasGENSTAT 5 (Genstat 5 Committee, 1993). ship with either CH -E / GEI or CH -E / DEI when4 4 using Eq. (IIa). However, when using Eqs. (IIb–c) feeding level and dietary factors were each sig-3. Results nificantly (P,0.001) related to CH -E / GEI or CH -4 4 E / DEI (Table 3). The relationship between CH -E /4 3.1. Difference between dairy and beef cattle GEI or CH -E / DEI and feeding level was negative,4 while the relationship between CH -E / GEI or CH -4 4 The data on diet type and CH -E for dairy and4 E / DEI and each of the dietary factors was positive. beef are presented separately in Table 2. There were An increase in feed intake of one level above no significant differences between dairy and beef maintenance would result in a reduction of pro-cattle in terms of SDMI/ TDMI (0.548 vs. 0.532, S.E. portionately 0.0078 or 0.0123 in CH -E / GEI or4 0.0210), TADFI/ TDMI (0.248 vs. 0.249, S.E. 0.0055) CH -E / DEI. However, increasing 0.10 of S4 DMI/ and SADFI/ TADFI (0.784 vs. 0.778, S.E. 0.0130). TDMI, TADFI/ TDMIor SADFI/ TADFI would result in an Animal type (dairy vs. beef) also had no significant increase of proportionately 0.0025, 0.0069 or 0.0048 effect on CH -E / GEI (0.068 vs. 0.069, S.E. 0.0020)4 in CH -E / GEI; or 0.0035, 0.0107 or 0.0067 in CH -4 4 or CH -E / DEI (0.089 vs. 0.090, S.E. 0.0017). These4 E / DEI.
two sets of data were then pooled together for all
subsequent analysis. Four beef cattle had a relatively 3.3. Methane energy output as a proportion of low CH -E / DEI (0.040–0.045), which were offered4 energy intake with feeding level and dietary
diets with low silage proportions (0.169–0.222) and factors
had relatively high feeding levels (1.75–2.37).
Simi-larly, the minimum range in CH -E / DEI for dairy4 The regression equations for these relationships cows was derived from those animals which were are presented in Table 3. When using Eq. (I), the given low silage (0.405–0.440) diets and had rela- relationship between CH -E and GEI or DEI was4
2
tively high feeding levels (3.25–3.46). significant (P,0.001) and the R value was high (0.846 or 0.841). The coefficient was 0.0547 or 3.2. Effect of digestibility, feeding level and 0.0714 and the constant 3.23 or 3.32. The
relation-dietary factors ship between CH -E and GEI or DEI was improved4 when feeding level above maintenance (FL-1) was
2
In the present study apparent energy digestibility added using Eq. (IIIa). The R values for the measured with cattle offered diets ad libitum (rang- relationships of CH -E with energy intake (GEI and4
Table 2
Variation between lactating dairy cows and beef steers
Cattle Mean S.D. Minimum Maximum
Methane energy / GE intake Dairy 0.068 0.0112 0.037 0.101
Beef 0.069 0.0176 0.029 0.101
Methane energy / DE intake Dairy 0.089 0.0148 0.051 0.130
Beef 0.090 0.0244 0.040 0.139
Silage DM / total DM intake Dairy 0.548 0.2120 0.181 1.000
Beef 0.532 0.2940 0.169 1.000
Total ADF / total DM intake Dairy 0.248 0.0536 0.131 0.372
Beef 0.249 0.0829 0.144 0.375
Silage ADF / Total ADF Dairy 0.784 0.1420 0.412 1.000
Table 3
Relationships between methane energy output and energy intake, feeding level or dietary factors (all relationships are significant (P,0.001) a
and the data in brackets in each equation are S.E. values)
2
Equations RSD R No.
CH -E4 5 0.0547 (0.0018) GEI13.2340 (0.5230) 3.016 0.846 (1)
0.0714 (0.0024) DEI13.3180 (0.5240) 3.032 0.841 (2)
CH -E / GEI4 5 20.0078 (0.0005) [FL-1]10.0877 (0.0016) 0.008 0.608 (3) 0.0252 (0.0028) SDMI/ TDMI10.0553 (0.0017) 0.012 0.431 (4) 0.0694 (0.0112) TADFI/ TDMI10.0522 (0.0029) 0.012 0.463 (5) 0.0476 (0.0039) SADFI/ TADFI10.0315 (0.0031) 0.011 0.463 (6)
CH -E / DEI4 5 20.0123 (0.0006) [FL-1]10.1203 (0.0021) 0.011 0.640 (7) 0.0346 (0.0038) SDMI/ TDMI10.0719 (0.0023) 0.016 0.402 (8) 0.1074 (0.0149) TADFI/ TDMI10.0646 (0.0038) 0.016 0.448 (9) 0.0665 (0.0053) SADFI/ TADFI10.0382 (0.0042) 0.015 0.445 (10)
a
RSD, residual standard deviation; CH -E, methane energy output (MJ / day); GEI, gross energy intake (MJ / day); DEI, digestible energy4 intake (MJ / day); FL, feeding levels (Agricultural and Food Research Council, 1990); SDMI, silage dry matter intake (kg / day); TDMI, total dry matter intake (kg / day); SADFI, silage acid detergent fibre intake (kg / day); TADFI, total acid detergent fibre intake (kg / day).
DEI) and feeding level (FL-1) were, respectively CH -E4 5
0.874 and 0.881. Feeding level had a significant DEI [0.096 (0.005)10.035 (0.005) SDMI/ TDMI]22.298 (0.161) (FL-1) 0.89 2.18 effect (P,0.001) on CH -E in each of these two4 (12) equations. A similar procedure was also applied to
dietary factors (SDMI/ TDMI, TADFI/ TDMI and SADFI/ where RSD is the residual standard deviation, the TADFI) for the relationship of CH -E with GEI or4 unit for CH -E and DEI is MJ / day and the data in4 DEI using Eq. (IIIb). This approach also improved brackets are S.E. values. Eqs. (11) and (12) each had the relationship between CH -E and GEI or DEI.4 a small constant (20.49 (S.E. 0.81) and20.63 (S.E.
2
The R values for these relationships ranged from 0.85) MJ / day, respectively). Because the constants 0.851 to 0.864. These three dietary factors each had had no significant effects on the predicted CH -E4 a significant effect on CH -E (P4 ,0.001). (MJ / day), they were adjusted to be zero. The S.E. The relationship of CH -E was finally examined4 value for the coefficient of each component in both using various combinations of energy intake (GE or equations was relatively small, indicating that each DE), feeding level above maintenance (FL-1) and component had a significant effect on CH -E (P,
4 dietary factor (SDMI/ TDMI, TADFI/ TDMI or SADFI/ 0.001). These two equations indicate that methane TADFI). A total of six combinations were examined production of cattle is proportional to DE intake and using Eq. (IV). The relationship between CH -E and4 is increased with increasing silage proportion in the GEI or DEI was further improved by addition of diet, while CH -E / DEI would reduce with
increas-4 2
both [FL-1] and a dietary factor. The R values were ing feeding level. If the ADF concentrations in all increased (0.879–0.888). The [FL-1] and dietary silages and concentrates are available, Eq. (11) factors each had a significant effect (P,0.001) on should be used as this equation gave a more accurate
2
CH -E in each of these 6 equations. Based on the R4 prediction than Eq. (12) when testing these equations value of the relationship and the accuracy of predic- using published data obtained with grass silage-based tion when testing all equations using published data diets (discussed later).
(discussed later), the following two equations are
recommended 3.4. Effect of live weight
CH -E4 5
2
R RSD The effects of live weights of animals were also DEI [0.094 (0.005)10.028 (0.005) SADFI/ TADFI]22.453 (0.159) (FL-1) 0.89 2.13 examined. CH -E (MJ / day) and daily intakes of GE
4
0.75
weight basis (kg ). All the above mentioned also been some studies which showed no reduction methods, where appropriate, were examined. There in methane production with increment of dietary were no improvements in the levels of significance forage levels, e.g. Beever et al. (1988) in beef cattle
2
or the R values of the equations. Therefore the offered grass silage diets.
effects of live weight of the cattle were not presented In the present study, CH -E / GEI and CH -E / DEI4 4 in the current paper. Holter and Young (1992) also were both related to SDMI/ TDMI, TADFI/ TDMI or reported no significant effect of live weight of SADFI/ TADFI. These relationships were all highly
2
lactating or dry dairy cows on CH -E in any of their4 significant with the R values ranging from 0.402 to six experiments. 0.463. This analysis indicated that an increase of 0.10 in SDMI/ TDMI, TADFI/ TDMI or SADFI/ TADFI would increase CH -E / GEI4 by proportionately 0.0025, 0.0069 or 0.0048; or CH -E / DEI by 0.0035,4 4. Discussion
0.0107 or 0.0067. A similar technique was also applied to a data set of 89 treatment means obtained The existing equations for predicting methane
in 27 dairy cow experiments published since 1969 production in cattle were developed from data in
(excluding those carried out at this Institute). In these animals offered diets containing mainly dried
for-studies a range of forages was used and the data on ages. The present data set with grass silage-based
feed composition, live weights of cows and milk diets is therefore relatively unique, and important to
production were also available. The relationships the industry where accurate prediction of CH -E and4 obtained with this set of data produced similar results hence ME intake are required.
to those derived from the present study. CH -E / DEI4 was, respectively increased by proportionately 4.1. Effect of forage proportion in the diet 0.0049, 0.0150 or 0.0086 with an increase of 0.10 of SDMI/ TDMI, TADFI/ TDMI or SADFI/ TADFI. These rela-Methane output in the rumen of animals is associ- tionships were all significant (P,0.001), although
2
2 Blaxter and Clapperton (1965). It is thus expected 0.0021) in CH -E / GEI or CH -E / DEI (R4 4 50.336 that the use of the earlier group of equations in or 0.373; P,0.001) as feed intake increased one general would under-predict CH -E for diets with4 level above maintenance, when using MEm calcu-high proportions of forage, but over-predict for diets lated from Agricultural and Food Research Council with high proportions of concentrates. (1990).
However, the prediction equations mentioned pre-4.2. Effect of feeding level viously, except the one of Blaxter and Clapperton (1965), did not consider the effect of feeding level An increase in feeding level can increase the on CH -E. Therefore, use of those equations which4 outflow rate of digesta in the rumen and leave less did not take account of the effect of feeding level in time available for microbial fermentation of the diet. general would under-predict CH -E for cattle at low4 The consequence is a reduction of nutrient de- planes of nutrition, while over-predict at high levels gradability in the rumen as well as methane pro- of feeding.
duction. Moe and Tyrrell (1979) reported that
in-creasing feeding level changed production rates of 4.3. Validation of the present Eqs. (11) and (12) CH -E from digestible soluble residues and digest-4
ible cellulose in diets of dairy cows. In a review of Eqs. (11) and (12) as recommended in the present studies in the literature with beef cattle, Johnson et study have been validated using published studies for al. (1991) reported that under most circumstances cattle offered grass silage-based diets (excluding increasing intake by one multiple of maintenance studies carried out at this Institute). These studies would reduce CH -E by proportionately 0.018 of4 included five lactating dairy cow experiments GEI. Blaxter and Clapperton (1965) reported a (Beever et al., 1989, 1991; Sutton et al., 1991, 1998; reduction in CH -E / GEI by b (where b4 50.050 DE / Unsworth et al., 1994) and one beef trial (Beever et GE20.0237) with increment of one feeding level al., 1988). A total of 36 treatments were presented in obtained in the combined data of sheep and beef these studies and the treatment mean data have been cattle given mostly non-grass silage diets, where used for the present validation. In these studies the DE / GE was measured at maintenance. This equation animals had a mean live weight of 526 kg, DE intake indicated that the effect of feeding level on CH -E4 of 202.7 MJ / day, CH -E of 19.5 MJ / day and FL of4 decreased as dietary energy digestibility at mainte- 3.25 (estimated from the Agricultural and Food nance reduced. Research Council, 1990. SDMI/ TDMI, TADFI/ TDMI In the present study the effect feeding level on and SADFI/ TADFI were averaged to be 0.541, 0.212 CH -E was obtained by, respectively relating CH -4 4 and 0.846, respectively. The validation indicated a E / GEI and CH -E / DEI to feeding level. These two4 significant relationship (P,0.001) between the actu-relationships were highly significant with CH -E /4 al (x) and predicted ( y) CH -E for both Eqs. (11) and4 GEI or CH -E / DEI (equations nos. (3) or (7) in4 (12) ( y50.915 (S.E. 0.0093)x for Eq. (11) (Fig. 1);
Fig. 1. Actual methane energy output against predicted methane energy output using present Eq. (11) on the published data of lactating cows and beef steers offered grass silage-based diets.
the mean value of remaining 27 treatments. Since Acknowledgements Eq. (11) gave a more accurate prediction than Eq.
(12), the former equation should be used if ADF The authors wish to thank their colleagues at the concentrations in both silage and concentrate are Agricultural Research Institute of Northern Ireland measured. for access to the calorimetric data used in the present
study.
5. Conclusion
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