Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 551134
Title Validation strategy can result in an overoptimistic view of the ability of milk infrared spectra to predict methane emission of dairy cattle
Author(s) Wang, Qiuyu; Bovenhuis, Henk
Source Journal of Dairy Science 102 (2019)7. - ISSN 0022-0302 - p. 6288 - 6295.
Department(s) Animal Breeding and Genomics
Publication type Refereed Article in a scientific journal
Publication year 2019
Keyword(s) CH emission - milk infrared spectroscopy - prediction - validation strategy

Because of the environmental impact of methane (CH 4 ), it is of great interest to reduce CH 4 emission of dairy cattle and selective breeding might contribute to this. However, this approach requires a rapid and inexpensive measurement technique that can be used to quantify CH 4 emission for a large number of individual dairy cows. Milk infrared (IR) spectroscopy has been proposed as a predictor for CH 4 emission. In this study, we investigated the feasibility of milk IR spectra to predict breath sensor–measured CH 4 of 801 dairy cows on 10 commercial farms. To evaluate the prediction equation, we used random and block cross validation. Using random cross validation, we found a validation coefficient of determination (R 2 val) of 0.49, which suggests that milk IR spectra are informative in predicting CH 4 emission. However, based on block cross validation, with farms as blocks, a negligible R 2 val of 0.01 was obtained, indicating that milk IR spectra cannot be used to predict CH 4 emission. Random cross validation thus results in an overoptimistic view of the ability of milk IR spectra to predict CH 4 emission of dairy cows. The difference between the validation strategies could be due to the confounding of farm and date of milk IR analysis, which introduces a correlation between batch effects on the IR analyses and farm-average CH 4 . Breath sensor–measured CH 4 is strongly influenced by farm-specific conditions, which magnifies the problem. Milk IR wavenumbers from water absorption regions, which are generally considered uninformative, showed moderate accuracy (R 2 val = 0.25) when based on random cross validation, but not when based on block cross validation (R 2 val = 0.03). These results indicate, therefore, that in the current study, random cross validation results in an overoptimistic view on the ability of milk IR spectra to predict CH 4 emission. We suggest prediction based on wavenumbers from water absorption regions as a negative control to identify potential dependence structures in the data.

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