Milk fatty acid profile and methane production in cattle fed grass- or grass-silage based diets.

We quantified relationships between methane production and milk FA profile in dairy cattle fed grass- or grass silage-based diets. Moderate to strong relationships between milk FA and methane yield or intensity were obtained, but those relationships largely differed from those for other types of diets.

In view of various mitigation options, there is a clear need for robust, inexpensive and simple measurement techniques to estimate enteric methane production in dairy cattle in commercial practice. The profile of FA in milk has been suggested as such a proxy measure for the prediction of enteric methane production. To study the relationship between milk FA profile and methane production in cattle fed grass- and grass silage-based diets, data from three studies were used, encompassing 4 grass herbage and 14 grass silage treatments and 132 individual cow observations in respiration chambers. Of the 42 milk FAs identified, no single FA had a strong positive correlation (r; strong correlation defined as |r| ≥ 0.50) with methane yield (g/kg DMI), and cis-12 C18:1 and cis-9,12,15 C18:3 had a strong negative correlation with methane yield. C14:0 iso, C15:0, C15:0 iso, C15:0 anteiso, C16:0, C20:0, cis-11,14 C20:2, cis-5,8,11,14 C20:4, C22:0, cis-7,10,13,16,19 C22:5 and C24:0 had a strong positive correlation with methane intensity (g/kg FPCM), and trans-15+cis-11 C18:1, cis-9 C18:1, and cis-11 C20:1 had a strong negative correlation with methane intensity. Relationships largely differed from those for other types of diets reported in literature. Therefore, milk FA profile as proxy measure for enteric methane may require diet-specific prediction equations.

The results of this research have been presented at the 6^th Greenhouse Gas and Animal Agriculture Conference (February 2016) in Melbourne, Australia, for which Jan Dijkstra received a travel-budget from METHAGENE.

Please find a link to the article in Animal Production Science here: http://www.publish.csiro.au/nid/72/paper/AN15509.htm

For more information, please contact: Jan.Dijkstra@wur.nl