254 T
. Yan et al. Livestock Production Science 64 2000 253 –263
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 been with lactating cows, which is approximately four
4
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 n 5247 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
compared to that of dried forages. This effect can A total of 322 cattle including 247 lactating dairy
shift the proportion of acetic acid in total VFAs cows and 75 beef steers were subjected to measure-
produced in the rumen, resulting in change of ments of energy metabolism in calorimetric cham-
methane production Ørskov and Ryle, 1990. An- bers at the Agricultural Research Institute of North-
derson and Jackson 1971 reported a consistently ern Ireland between 1992 and 1997. The dairy cattle
higher proportion of acetic acid in total VFAs in the were Holstein Friesian cows and the beef cattle were
rumen of sheep offered grass silage rather than grass Charolais cross, Simmental cross and Aberdeen
hay. The CH -E was found to account for a higher Angus cross steers. The dairy cows were drawn from
4
proportion over GE intake or digestible energy DE ten feeding experiments Cushnahan et al., 1995;
intake in dairy cattle offered diets based on grass Gordon et al., 1995a,b, 2000; Carrick et al., 1996;
silages, rather than dried grass Yan et al., 1997b. Yan et al., 1996, 1997b; Keady and Mayne, 1998;
As a consequence, the prediction of CH -E output Ferris et al., 1999; C.S. Mayne, personal communi-
4
with grass silage-based diets using the equations cation, and the beef cattle were obtained from 3
developed from the non-grass silage-based diets, feeding experiments Kirkpatrick, 1995; Kirkpatrick
may result in considerable error in the calculation of et al., 1997; Lavery, 1998. In each experiment the
ME intake for animals. Therefore, there is a need to animals were offered the experimental diets for at
examine these effects with grass silage-based diets. least 3 weeks in individual feeding accommodation
In addition to differences in diet, there are also before measurement of energy metabolism. In the
T . Yan et al. Livestock Production Science 64 2000 253 –263
255
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 n 5275 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
The relationship between CH -E and energy in-
4
A total of 30 perennial ryegrass silages were take and or other variables was examined on the
examined over the 13 experiments. The silages combined data of dairy and beef cattle in four steps.
encompassed primary growth and first and second Firstly, CH -E was related to total GE intake GEI
4
regrowth material. The grass was either unwilted or and digestible energy DE intake DEI using the
wilted prior to ensiling and ensiled with or without linear regression technique Eq. I. Secondly, CH -
4
application of silage additives. All silages were well E was calculated as CH -E GEI and CH -E DEI.
4 4
preserved with silage dry matter DM concentration These two variables were then each related to FL,
at feeding ranging from 168 to 398 g kg Table 1. apparent energy digestibility, silage DM intake
256 T
. Yan et al. Livestock Production Science 64 2000 253 –263 Table 1
Data on animal, diet and energy metabolism for both dairy and beef cattle Mean
S.D. Minimum
Maximum Cattle n 5322
Live weight kg 563
58.9 416
733
a
Milk yield kg day 23.2
8.07 3.2
49.1 Silage composition n 530
Dry matter g kg 223
55.1 168
398 pH
3.95 0.336
3.60 4.75
NH -N total-N g kg 91
60.3 22
240
3
Crude protein g kg DM 145
26.8 97
193 Gross energy MJ kg DM
18.7 0.53
17.8 20.0
Ash g kg DM 87
13.6 66
117 Acid detergent fibre g kg DM
375 53.9
301 486
Total diet n 5322 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 n 5322
Gross energy intake 271.9
92.34 105.5
454.6 Digestible energy intake
207.0 70.58
79.5 351.6
Metabolisable energy intake 177.4
61.81 66.1
311.2 Methane energy output
18.1 5.88
4.1 29.6
a
For dairy cows only n 5247.
S as a proportion of total DM intake T
CH -E 5 a 1 b ? intake 1 c ? [FL-1] IIIa
DMI DMI
4
S T
, total ADF intake T as a propor-
DMI DMI
ADFI
tion of T T
T , and silage ADF intake
CH -E 5 a 1 intake ? b 1 c ? [dietary factor] IIIb
DMI ADFI
DMI 4
S as a proportion of T
S T
Eqs.
ADFI ADFI
ADFI ADFI
IIa–c. Thirdly, CH -E was related to energy intake CH -E 5 a 1 intake ? b 1 c ? [dietary factor]
4 4
GE or DE and FL above maintenance FL-1 or 1 d FL-1
IV dietary factor T
T , S
T or S
ADFI DMI
DMI DMI
ADFI
T Eqs. IIIa–b. Finally, CH -E was predicted
ADFI 4
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 T T
, S T
or S T
y 5 a 1 b1 ? x1
ADFI DMI
DMI DMI
ADFI ADFI
i
Eq. IV y 5 a 1 b1 ? x1 1 b2 ? x2
i
y 5 a 1 b1 ? x1 1 b2 ? x2 1 b3 ? x3
i
CH -E 5 a 1 b ? intake I
4
where a represents the effect of experiment i for
i
i51 to 13, x1, x2, and x3 are the x-variables and b1, CH -E intake 5 a 1 b ? digestibility
IIa
4
b2 and b3 are their regression coefficients. The feeding level FL is estimated as multiples of ME
CH -E intake 5 a 1 b ? [FL-1] IIb
4
intake MEI over ME requirement for maintenance ME MEI ME , where ME
was calculated
m m
m
CH -E intake 5 a 1 b ? [dietary factor] IIc
from the equations of the Agricultural and Food
4
T . Yan et al. Livestock Production Science 64 2000 253 –263
257
Research Council 1990. The statistical programme ing from 0.639 to 0.847 had no significant relation-
used was
GENSTAT
5 Genstat 5 Committee, 1993. ship with either CH -E GEI or CH -E DEI when
4 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 -
