The Journal of Agricultural Science

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The Journal of Agricultural Science (2010), 148:55-72 Cambridge University Press
Copyright © Cambridge University Press 2009
doi:10.1017/S0021859609990499

Modelling Animal Systems Paper

Simulating the effects of grassland management and grass ensiling on methane emission from lactating cows


A. BANNINKa1 c1, M. C. J. SMITSa1, E. KEBREABa2, J. A. N. MILLSa3, J. L. ELLISa4, A. KLOPa1, J. FRANCEa4 and J. DIJKSTRAa5

a1 Department of Animal Production, Animal Sciences Group, Edelhertweg 15, 8219 PH Lelystad, The Netherlands
a2 Department of Animal Science, University of California, Davis CA 95616, USA
a3 School of Agriculture, Policy and Development, University of Reading, Earley Gate, Reading RG6 6AR, UK
a4 Centre for Nutrition Modelling, University of Guelph, Guelph, Ontario N1G 2W1, Canada
a5 Animal Nutrition Group, Wageningen University, Marijkeweg 40, 6709 PG Wageningen, The Netherlands
Article author query
bannink a [PubMed]  [Google Scholar]
smits mcj [PubMed]  [Google Scholar]
kebreab e [PubMed]  [Google Scholar]
mills jan [PubMed]  [Google Scholar]
ellis jl [PubMed]  [Google Scholar]
klop a [PubMed]  [Google Scholar]
france j [PubMed]  [Google Scholar]
dijkstra j [PubMed]  [Google Scholar]

SUMMARY

A dynamic, mechanistic model of enteric fermentation was used to investigate the effect of type and quality of grass forage, dry matter intake (DMI) and proportion of concentrates in dietary dry matter (DM) on variation in methane (CH4) emission from enteric fermentation in dairy cows. The model represents substrate degradation and microbial fermentation processes in rumen and hindgut and, in particular, the effects of type of substrate fermented and of pH on the production of individual volatile fatty acids and CH4 as end-products of fermentation. Effects of type and quality of fresh and ensiled grass were evaluated by distinguishing two N fertilization rates of grassland and two stages of grass maturity. Simulation results indicated a strong impact of the amount and type of grass consumed on CH4 emission, with a maximum difference (across all forage types and all levels of DMI) of 49 and 77% in g CH4/kg fat and protein corrected milk (FCM) for diets with a proportion of concentrates in dietary DM of 0·1 and 0·4, respectively (values ranging from 10·2 to 19·5 g CH4/kg FCM). The lowest emission was established for early cut, high fertilized grass silage (GS) and high fertilized grass herbage (GH). The highest emission was found for late cut, low-fertilized GS. The N fertilization rate had the largest impact, followed by stage of grass maturity at harvesting and by the distinction between GH and GS. Emission expressed in g CH4/kg FCM declined on average 14% with an increase of DMI from 14 to 18 kg/day for grass forage diets with a proportion of concentrates of 0·1, and on average 29% with an increase of DMI from 14 to 23 kg/day for diets with a proportion of concentrates of 0·4. Simulation results indicated that a high proportion of concentrates in dietary DM may lead to a further reduction of CH4 emission per kg FCM mainly as a result of a higher DMI and milk yield, in comparison to low concentrate diets. Simulation results were evaluated against independent data obtained at three different laboratories in indirect calorimetry trials with cows consuming GH mainly. The model predicted the average of observed values reasonably, but systematic deviations remained between individual laboratories and root mean squared prediction error was a proportion of 0·12 of the observed mean. Both observed and predicted emission expressed in g CH4/kg DM intake decreased upon an increase in dietary N:organic matter (OM) ratio. The model reproduced reasonably well the variation in measured CH4 emission in cattle sheds on Dutch dairy farms and indicated that on average a fraction of 0·28 of the total emissions must have originated from manure under these circumstances.

(Received July 20 2009)

(Online publication December 07 2009)

Correspondence:

c1 To whom all correspondence should be addressed. Email: andre.bannink@wur.nl


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