Corn coproducts are readily available as animal feedstuffs and they are often added to livestock diets as a source of protein and energy. The protein supplied can be degraded in the rumen to a variable extent, depending on the coproduct, while energy is provided by fat and fermentable fiber. The corn wet milling process consists of steeping the raw corn to moisten and soften the kernels, milling, and then separating the kernel components through processes including washing, screening, filtering, and centrifuging. The primary end products obtained from corn wet milling are industrial corn starch, which is utilized for sweeteners, corn oil, and ethanol.
Additional end products from the wet milling process include several feed coproducts, including corn gluten feed (CGF), corn gluten meal (CGM), corn germ meal, and condensed fermented corn extractives. The feed coproduct streams from corn wet milling account for approximately 30% of the raw corn input (typically 24% is converted into CGF while about 6% ends up as CGM); nearly 66% of the corn kernel is converted into starch; and 4% ends up as corn oil.
Corn gluten meal vs. fermented corn gluten meal
Dry and wet CGM has high protein concentration (approximately 60%, w/w), with good concentration of methionine but relatively deficient in lysine. Its low total track digestibility limits its use in pre-weaned calves, since their rumen is not completely developed. It has been reported that peptides remaining from fermented corn gluten meal (FCGM) are strong antioxidants in vitro and increase the immune function in vivo. It has been reported that probiotics in the wet FCGM improve growth, antioxidant and immune capacity of post-weaned calves, it remains to be seen if these effects are also repeatable during pre-weaning.