We’ve previously discussed high-shear dry extrusion of corn and how this process can be used to form highly-gelatinized starch that is quickly degraded in the rumen. Among other things, dry extruded corn has more available energy for productive purposes. This means that more of the energy in corn, following dry extrusion, can be used by dairy cows to produce milk.
But what else can happen when high-gelatinized, easily broken-down starch is fed to dairy cows? All cattle are ruminants, which indicates that all of them have a rumen. The rumen is a massive microbial fermentation vat, and the microbes help the ruminants extract nutrients from ingredients in feed in unique ways. People have spent their entire careers exploring and studying rumen function, so at the risk of minimizing their work, microbes in the rumen degrade nutrients and cause the formation of volatile fatty acids, in particular, acetate, propionate, and butyrate. These volatile fatty acids (also called short-chain fatty acids) are used as an energy source, first and foremost by the rumen itself, which is a good thing because keeping the entire rumen operating, tissues and all, requires a lot of energy. However, the composition and amount of volatile fatty acids also are important for things like the formation of milk fat in the mammary gland. So, having the right amounts of volatile fatty acids affects what dairy producers can sell at the end of the day.
But focusing on the energy side of things, while vitally important, is only part of the story. While boosting what happens in the rumen with the use of highly gelatinized starch, this fact ignores, in part, how this is achieved. The rumen microbes are better able to form volatile fatty acids partly because there are more of them. Again, this is overly simplified, but the rumen microbes are able to multiply in number because they can better use starch when highly gelatinized.
Eventually, the rumen microbes spill over from the rumen and enter the rest of the digestive tract, now able to be used as a source of protein by the dairy cow. The dry portion of bacteria is over 50% protein.
So, with highly gelatinized starch from corn, achieved with the high-shear dry extrusion process, ruminants can take starch and convert it to some of their own protein with the help of rumen microbes, such as bacteria. Considering that corn is often 1/3 or less the price of excellent protein meals, like soy meal, this offers an attractive way to get your dairy cows to make some of their own protein for milk production.