Comparing grains with Palm Kernel Expeller Meal (PKE)

Which is the better feed for dairy cows?
Grains (wheat, barley, maize) and PKE are all very different feeds and decisions about which feed will best suit a lactating dairy herd depends on what cows require at any given time during the season as well as practical issues, such as ways that you can deliver these feeds to the cow.

How can we compare each feed with what a cow needs?
Feeding a cow well means balancing the diet with the range of feeds available, to provide a diet as close to the ideal requirements as you can. A general description on each of the feed components is as follows:

A general description on each of the feed components can be found on this downloadable PDF.