Milk Fatty Acids Estimation by Mid-Infrared Spectroscopy as Proxy for Prediction of Methane Emission in Dairy Cows

Abstract

Ruminant enteric methane (CH₄) emission contributes to global warming. Current enteric CH₄ measurement techniques, such as whole-animal chambers and tracer gas techniques require complex instrumentation and, thus, are limited in their use. Thus, a simple, robust and inexpensive measurement technique applicable on a large scale to estimate CH₄ emission from dairy cattle would therefore be valuable. Milk fatty acid (MFA) composition has been suggested as a means of predicting enteric CH₄ output in lactating dairy cattle because of the common biochemical pathways among CH₄ and fatty acids in the rumen. A summary of studies that investigated the predictive power of MFA composition for CH₄ emission indicated good potential, with predictive power ranging between 47 and 95%. Until recently, gas chromatography (GC) was the principal method used to determine the MFA profile, but GC is unsuitable for routine analysis. This has led to the application of mid-infrared (MIR) spectroscopy. The major advantages of using MIR spectroscopy to predict CH₄ emission include its simplicity and potential practical application at large scale. Disadvantages include the inability to predict important MFA for CH₄ prediction, and the moderate predictive power for CH₄ emission. It may not be sufficient to predict CH₄ emission based on MIR alone. Integration with other factors, like feed intake, nutrient composition of the feed, parity, and lactation stage may improve the prediction of CH₄ emission using MIR spectra.