How does a cow use energy from corn?

Answer 1

Actually, it's not the cow that directly uses the energy from the corn she is fed, but rather it's the microbes in her rumen that have access to it first. Microbes use the energy--in the form of starch, which is made up of carbohydrate--for growth and reproduction and to convert carbohydrates into volatile fatty acids, three of which are proprionate, acetate and butyrate. Proprionate is the most sought-after VFA for beef and dairy production as it is what helps an animal meet its energy requirements. By-pass starch, which gets digested in the abomasum and reabsorbed in the small intestine, is also used for energy by the cow.

Such VFAs and by-pass starch are used by the cow for maintenance, growth, production (such as producing milk [dairy cows] or meat [beef cattle]), and reproduction in that order. Excess energy is converted and stored into fat, such which is often seen in feedlot cattle when they are fed an 85 percent ration of grain which may be or include corn. Dairy cows will readily convert the energy they get from corn into milk, and use that energy for meeting reproductive requirements: this also applies to beef cows.

Energy from corn is used in meeting maintenance requirements (rebuild/repair muscle/skin/fat tissue, homeostasis, cell function, metabolic rate, etc.), reproductive needs (milk, normal reproductive function, normal estrous cycles [or for males, normal sperm growth, seminal fluid, and libido]), growth (in growing animals, and growing muscle, bone, fat, skin, etc.), normal body functions (eating, defecating, urinating, moving around, socializing with other cows, awareness of surroundings, etc.), and many other things.