Megalac is a rumen protected fat, combining natural plant oil (palm fatty acids) with calcium.
The calcium protects the fat from breaking down in the rumen, so unlike many other fats there is no negative effect on rumen function. The fat is then digested in the acidic lower gut, with near 100% efficiency. The cow then uses the energy in Megalac for milk production and performance.
Megalac has the highest independently measured net energy value of any feedstuff.