These uses result in numerous byproduct ingredients available for the feed industry, such as corn gluten meal, corn gluten feed, corn germ meal and corn distillers grains (DDGS). These byproducts increase the opportunity for corn to be used in dairy rations, meaning many rations contain multiple sources of corn.
Corn and its byproducts are generally rich sources of energy and are highly digestible. Corn silage in particular provides much more energy than other forage crops. Since corn is also a high-yielding crop, these ingredients are normally affordable compared to other grains and grain byproducts.
In addition to energy, corn and corn byproducts provide a significant part of the total protein a dairy cow receives. Unfortunately, the amino acid balance of this source of protein is less than ideal for dairy cows.
A well-balanced diet provides all of the essential amino acids a cow needs with minimum overage. When amino acids are poorly balanced, two scenarios are possible:
- Cows do not receive enough essential amino acids to reach peak milk production.
- Some amino acids must be fed in excess in order to satisfy the first limiting amino acid, which leads to waste.
Neither situation is desirable for a cow. If amino acids are deficient, the cow struggles to make milk and to meet other protein requirements like supporting its immune system or muscle growth.
Conversely, if all of a cow’s amino acid needs are met but the cow has an overage of protein in order to meet these needs, then it must expend energy to get rid of the unwanted extra protein.
Ten amino acids are considered essential: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine, and these are listed in Table 1 for several ingredients.
(Tryptophan was intentionally not included in the table because tabular data for some of the ingredients did not include this amino acid.) These amino acids must be made available to the cow through the diet or from the rumen microbes in order to properly function.
The similarities in amino acid profiles for all of the corn products and byproducts may not be apparent to the untrained eye. Corn products contain very large amounts of the amino acid leucine. Unfortunately, this amino acid, while essential, is generally not among the most limiting in livestock diets.
On the other hand, all of the corn products are low relative to dairy cow requirements for milk production, in arginine, histidine and lysine, and marginal in methionine. This means these amino acids need to be provided by ration ingredients rich in these nutrients to offset the deficiency in corn.
It is not unusual for some forages, such as alfalfa, to also provide a portion of the ration protein in cows’ diets in Canada and the U.S. Alfalfa is an excellent source of arginine and contains more lysine than corn but less histidine and methionine than many of the corn products. For this reason, alfalfa shouldn’t be used as a sole solution for balancing the corn amino acid profile.
Along with DDGS, the most readily available vegetable proteins are canola meal and soybean meal. Canola meal complements corn protein by supplying arginine, histidine and lysine along with similar to slightly higher amounts of methionine.
Soybean meal is a good source of arginine and lysine, with concentrations of histidine similar to corn but, like alfalfa, is low in methionine.
While corn protein sources like DDGS may be economical, it can be advantageous and more efficient to substitute some of the corn protein with protein from other ingredients in order to better balance amino acids.
Table 2 provides results from a study in which portions of the corn protein in the diets were replaced with canola meal.
The diets were formulated to contain 15 percent crude protein. Corn was the major source of grain and provided about 35 percent of the total diet. At 10 percent crude protein, the corn grain contributed 3.5 percent protein to the diet.
The diet also contained 27.5 percent corn silage. At 9.5 percent crude protein, this ingredient supplied another 2.6 percent protein to the diet.
The control diet contained 10.5 percent DDGS, and this ingredient had 32 percent crude protein, donating another 3.3 percent protein to the formula. Thus, the control ration had 63 percent of the total protein from corn (9.4 percent of the 15 percent).
With Test Diet 1, one-third of the protein from DDGS was substituted with protein from canola meal. With this small change, equivalent to 1.1 percent of protein in the diet (3.3 percent provided by DDGS divided by three), milk components tended to increase.
With Test Diet 2, two-thirds of the protein from DDGS was substituted with protein from canola meal. Milk production and milk components increased, and feed efficiency was improved with this formulation.
The efficiency of protein usage also increased with this diet. This involved removing only 2.2 percent of the total ration protein supplied by a corn product with protein from another source – in this case, canola meal.
Corn remains a staple in diets for dairy cows and will continue to provide a large part of the protein cows receive. Balancing corn with complementary proteins, such as canola meal, allows nutritionists to maximize the use of corn in efficient rations. PD
To learn more about canola meal and its amino acid profile, visit Canolamazing.
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Essi Evans
- Technical Advisory Services Inc.
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