Short communication: Development of an equation for estimating methane emissions of dairy cows from milk Fourier transform mid-infrared spectra by using reference data obtained exclusively from respiration chambers
Date
2018-05-09
Journal Title
Journal ISSN
Volume Title
Publisher
FASS Inc. and Elsevier Inc.
Abstract
Evaluation and mitigation of enteric methane (CH4)
emissions from ruminant livestock, in particular from
dairy cows, have acquired global importance for sustainable,
climate-smart cattle production. Based on
CH4 reference measurements obtained with the SF6
tracer technique to determine ruminal CH4 production,
a current equation permits evaluation of individual daily
CH4 emissions of dairy cows based on milk Fourier
transform mid-infrared (FT-MIR) spectra. However,
the respiration chamber (RC) technique is considered to
be more accurate than SF6 to measure CH4 production
from cattle. This study aimed to develop an equation
that allows estimating CH4 emissions of lactating cows
recorded in an RC from corresponding milk FT-MIR
spectra and to challenge its robustness and relevance
through validation processes and its application on a
milk spectral database. This would permit confirming
the conclusions drawn with the existing equation
based on SF6 reference measurements regarding the
potential to estimate daily CH4 emissions of dairy cows
from milk FT-MIR spectra. A total of 584 RC reference
CH4 measurements (mean ± standard deviation
of 400 ± 72 g of CH4/d) and corresponding standardized
milk mid-infrared spectra were obtained from 148
individual lactating cows between 7 and 321 d in milk
in 5 European countries (Germany, Switzerland, Denmark,
France, and Northern Ireland). The developed
equation based on RC measurements showed calibration
and cross-validation coefficients of determination
of 0.65 and 0.57, respectively, which is lower than
those obtained earlier by the equation based on 532
SF6 measurements (0.74 and 0.70, respectively). This
means that the RC-based model is unable to explain
the variability observed in the corresponding reference
data as well as the SF6-based model. The standard errors
of calibration and cross-validation were lower for
the RC model (43 and 47 g/d vs. 66 and 70 g/d for the
SF6 version, respectively), indicating that the model
based on RC data was closer to actual values. The root
mean squared error (RMSE) of calibration of 42 g/d
represents only 10% of the overall daily CH4 production,
which is 23 g/d lower than the RMSE for the SF6-
based equation. During the external validation step an
RMSE of 62 g/d was observed. When the RC equation
was applied to a standardized spectral database of milk
recordings collected in the Walloon region of Belgium
between January 2012 and December 2017 (1,515,137
spectra from 132,658 lactating cows in 1,176 different
herds), an average ± standard deviation of 446 ± 51 g
of CH4/d was estimated, which is consistent with the
range of the values measured using both RC and SF6
techniques. This study confirmed that milk FT-MIR
spectra could be used as a potential proxy to estimate
daily CH4 emissions from dairy cows provided that the
variability to predict is covered by the model.
Description
Publication history: Accepted - 1 April 2018; Published online - 9 May 2018.
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Article
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Keywords
cattle, greenhouse gas, spectroscopy, proxy
Citation
Vanlierde, A., Soyeurt, H., Gengler, N., Colinet, F. G., Froidmont, E., Kreuzer, M., Grandl, F., Bell, M., Lund, P., Olijhoek, D. W., Eugène, M., Martin, C., Kuhla, B. and Dehareng, F. (2018) ‘Short communication: Development of an equation for estimating methane emissions of dairy cows from milk Fourier transform mid-infrared spectra by using reference data obtained exclusively from respiration chambers’, Journal of Dairy Science, 101(8), pp. 7618–7624. doi: 10.3168/jds.2018-14472.