This post is for bruce. It's a copy paste of the table from:
Elgersma, A., S. Tamminga, and G. Ellen. 2003. Effect of grazing versus stall-feeding of cut grass on milk fatty acid composition of dairy cows. Proceedings of the Int. Occ. Symp. of the European Grassland Federation, Pleven, Bulgaria, May 2003. Grassland Science in Europe 8: 271-274.
I've no idea where I got the pdf from, it's just been lying around on my hard drive for ages. Not on pubmed.
The PUFA varied from 4.34 to 5.76, in the same 6 cows over a 5 month period. I don't really think of diet components in terms of accuracy to two decimal places. The figure of 5% is somewhere in the middle. My own PUFA intake estimate comes as total PUFA value from Fitday, so is USA based and probably bears little resemblance to values from parts of the world where cows are fed on grass! My estimate varies between 10 and 20g/d, depending on menu and how much I believe Fitday represents UK food. Even using http://www.nutritiondata.com/ the values in various types of cream and butter are wildly variable in their PUFA ratios. I just feel we can never really know exactly what is in a specific block of butter... Keeping it low is good, how low is low? I really dunno what I eat!
Sorry the table's a bit small, that's how it copy pasted
PS thanks for the reading pointers. Bear I've read, but not Peat.