Corn, a staple grain in many diets worldwide, is often recognized for its carbohydrate content. However, understanding the protein content of corn is crucial for balanced nutrition, especially when considering its role in animal feed or human diets. This article delves into the protein levels found in corn, comparing it to other grains and exploring the factors that can influence its nutritional value.
Protein Content Compared to Other Grains
When compared to other common feed grains, corn generally contains a lower protein percentage while offering a slightly higher energy content. The following table illustrates this comparison:
| Barley | Corn | Wheat | Oats | Sorghum | Field Peas | |
|---|---|---|---|---|---|---|
| Dry Matter Basis | ||||||
| Energy | ||||||
| TDN, % | 84.1 | 87.6 | 86.8 | 83.0 | 86.0 | 80.0 |
| NEm (Mcal/kg) | 2.06 | 2.17 | 2.15 | 2.03 | 2.12 | 1.94 |
| NEg (Mcal/kg) | 1.40 | 1.49 | 1.47 | 1.37 | 1.45 | 1.30 |
| Protein | ||||||
| Crude Protein (%) | 12.8 | 8.8 | 13.8 | 12.6 | 11.6 | 23.9 |
| Undegradable protein (% of CP) | 50.8 | 65.3 | 35.6 | 56.5 | 71.1 | 15.5 |
| Fiber | ||||||
| Neutral detergent fiber (%) | 18.3 | 9.7 | 12.4 | 26.7 | 7.2 | 13.7 |
| Acid Detergent fiber (%) | 7.1 | 3.6 | 4.2 | 13.3 | 4.6 | 9.2 |
| Source: National Academy of Sciences, Engineering, and Medicine, 2016 TDN = Total Digestible nutrients NEm = Net energy for maintenance NEg = Neg energy for gain |
As shown, corn contains approximately 8.8% crude protein on a dry matter basis, lower than barley, wheat, oats, and sorghum. Field peas contain significantly more protein. This makes corn a valuable energy source, primarily due to its high starch content (around 72% on a dry-matter basis).
Understanding Protein Digestibility in Corn
Not all protein is created equal, especially when it comes to digestibility. In corn, approximately 65% of the protein is “escape protein,” also known as bypass protein. This means it escapes fermentation in the rumen (in animals like cattle) and is instead digested and absorbed in the small intestine. The remaining 35% is rumen-degradable protein, essential for ruminal microorganisms to grow and synthesize their own proteins.
This distinction is important because animals, particularly ruminants, require both types of protein for optimal health and growth. Diets high in corn often benefit from supplemental rumen-degradable protein.
Optimizing Protein in Corn-Based Diets for Animals
For backgrounding or finishing diets that heavily rely on corn, supplemental rumen-degradable protein is often necessary. This can be achieved through:
- Nonprotein nitrogen sources (urea or biuret)
- Natural protein sources (sunflower meal, canola meal, or soybean meal)
- A combination of both
Supplementation ensures that the ruminal microorganisms have sufficient nutrients to thrive, ultimately benefiting the animal’s overall protein utilization.
Mineral Content of Corn and Dietary Considerations
Like other cereal grains, corn is relatively low in calcium but high in phosphorus. This imbalance can lead to health issues, particularly urinary calculi in animals. To prevent these problems, diets high in corn should include a supplemental calcium source, such as limestone.
The recommended calcium-to-phosphorus ratio in backgrounding and feedlot diets is a minimum of 2:1 (two parts calcium to one part phosphorus) to maintain proper mineral balance.
Impact of Harvesting, Storage, and Processing on Protein Content
Different methods of harvesting, storing, or processing corn can slightly affect its nutrient content, but the variations are generally not substantial.
| Corn Type | Dry Matter | TDN, % | NEm, Mcal/lb | NEg, Mcal/lb | CP, % | Escape Protein, % of CP |
|---|---|---|---|---|---|---|
| Dry rolled corn | 87 | 88 | 0.99 | 0.68 | 8.8 | 65 |
| High-moisture corn | 70 | 90 | 1.02 | 0.71 | 8.8 | 55 |
| Steam-flaked corn | 81 | 95 | 1.08 | 0.76 | 8.5 | 70 |
| Ear corn | 83 | 85 | 0.95 | 0.64 | 8.3 | 64 |
| Earlage | 63 | 84 | 0.95 | 0.64 | 8.1 | 49 |
| Snaplage | 59 | 82 | 0.91 | 0.61 | 8.1 | 45 |
| Source: Nation Academy of Sciences, Engineering, and Medicine 2016 |
While methods like stream-flaking may slightly increase the digestibility and energy content, the protein percentage remains relatively consistent across different forms of corn.
Conclusion
While corn may not be the highest protein source among grains, understanding its protein content, digestibility, and mineral composition is vital for creating balanced and nutritious diets, especially in animal feed applications. Supplementation with rumen-degradable protein and calcium can optimize the nutritional value of corn-based diets, ensuring the health and productivity of livestock. Always consider the specific needs of the animal or individual when formulating diets around corn.
