Corn grain is the energy standard among all feedstuffs fed to cattle. It is an energy-dense feed, second only to oils, fats, or other feedstuffs rich in lipids.
Corn has traditionally been priced and sold per ton or by the bushel. That’s because it has long been a feedstuff with homogeneous nutrient concentration, containing approximately 9% to 10% protein, 60% starch, and 3% oil on a dry matter (DM) basis. Some modern corn hybrids differ significantly and contain 8% protein, around 70% starch, and almost 4% oil.
However, it’s not just the starch concentration that’s important. The true value is really found when measuring starch levels digested by the cow.
Prolamins are proteins associated with the starch in corn and other cereal grains protecting the starch granules from enzymatic degradation. Prolamin in corn (zein) comprises 50% to 60% of all protein in the kernel and is cross-linked, encapsulating starch into water-tight globules.
The starch present in vitreous corn is more intricately associated with prolamin, improves its hydrophobicity, and thus reduces the accessibility of starch-degrading enzymes. Prolamin is responsible for this vitreous (glass-like) characteristic of certain corn hybrids that determine their digestibility, and thus how much energy livestock can obtain from it. Research at the University of Wisconsin has demonstrated that starch digestibility fell by 0.86 percentage units per percentage unit gain in grain prolamin (expressed as percent of starch).
Continue reading this article published in Hoard’s Dairyman.
