Understanding feed ingredients typically used in feed mills
Feed ingredients are the major cost in animal production and their physical and nutritional quality should be monitored on a regular basis to ensure good animal health and performance.
By Wilmer Pacheco, Charles Stark, and Adam Fahrenholz
Feed cost represents around 70% of the total cost in livestock production and can be divided into ingredient and processing costs. The cost associated with processing can vary based on several factors such as scale and type of operation (commercial vs. integrated), types of feeds produced (e.g., broilers, layers, swine, and aquaculture), and equipment and local market conditions (e.g., price of electricity and natural gas). Processing costs can also include labor (e.g., management, administrative, and operative personnel), maintenance and repairs, utilities (e.g., electricity and fuel), transportation, regulatory compliance, equipment depreciation, and quality control, among others.
The price of raw ingredients such as grains, protein sources, liquid ingredients, vitamins and mineral premixes, synthetic amino acids, and other feed additives represents the majority of feed cost. In addition, the prices of feed ingredients fluctuate based on availability and market conditions. In this article, we will discuss some of the most common ingredients used in the feed mill.
Corn and soybean meal typically represent the largest percentage of a feed formula in the United States because they are readily available and complement each other nutritionally. Corn is a good source of energy in the form of carbohydrates (e.g., starch), while soybean meal is a good source of protein and provides essential amino acids necessary for growth and production. Corn is graded using a grading standard set by the U.S. Department of Agriculture (USDA) based on factors such as damaged kernels, presence of foreign material, and bulk density measured in bushels (as the grade decreases in quality from 1 to 5, bulk density decreases). The feed industry typically uses U.S. grade No. 2, with a minimum test weight per bushel of 54 pounds and a maximum limit of 5% total damaged kernels, and 3% of broken corn and foreign material (BCFM). Because corn is also used in wet and dry milling to produce other products such as corn oil, corn syrup, dextrose, and ethanol, there are by-products such as corn gluten meal and distillers dried grains with solubles (DDGS) which are available for use in livestock diets. Corn gluten meal is a by-product of wet milling and is a good source of protein. In the dry milling process used to produce ethanol, corn is initially ground to increase its surface area, its starch is broken down into single glucose molecules using amylolytic enzymes, and then yeast is used to ferment the glucose. Since corn contains roughly 70% starch, most of which is converted to ethanol, the rest of the nutrients in the corn kernel are concentrated approximately three times in the by-product DDGS. Therefore, DDGS are a good source of protein, fat, and minerals in livestock feeds. However, it is important to measure the nutritional composition of DDGS, as it can be quite variable depending on grain source and processing facility.
Wheat can also be used in livestock diets when its price is competitive compared to corn and/or when pellet quality and stability in water is important (e.g., shrimp feed). Wheat contains more protein than corn and it is generally described as being of winter or spring variety, is referred to as being white or red depending on its seed coat color, and is classified as hard or soft wheat depending on the characteristics of its endosperm (e.g., crystalline, amorphous, or vitreous). Wheat-based diets typically result in higher pellet durability compared to corn-based diets. Natural or synthetic pigments may be required in wheat-based diets to compensate for its lack of pigments if enhancing the color/pigmentation of the final product is important. The primary use of wheat is the production of flour for use in human food. In the flour milling process, the starchy endosperm is separated from the other components of the wheat kernel. Wheat middlings are one of the most common by-products from flour milling, and includes fine particles of bran, germ, and flour (fully separated wheat bran and wheat germ are also available to the livestock feed industry.) Wheat middlings are commonly used in diets with lower energy density such as diets for layers and broiler breeders. It is also worth noting that, since by-products like wheat middlings have a lower physical bulk density than corn, soybean meal, and other common ingredients, it is important to pay attention to overall diet bulk density to ensure that the mixer is not over-filled, which can lead to poor mixing uniformity.
Soybean meal is a by-product of solvent soybean oil extraction or extrusion-expeller oil extraction. Soybean meal is a protein-rich feed ingredient and contains 0.5 to 9% of oil depending on the process used to extract the oil. Removal of the hulls prior to soybean processing influences the level of protein of the final product; dehulled solvent extracted meal contains around 48% crude protein and lower fiber content compared to hulled soybean meal which contains around 44% crude protein. Soybean meal needs to be properly heat-treated to remove anti-nutritional factors such as trypsin inhibitors and increase its nutritional value. Since trypsin inhibitors are difficult to measure, there are indirect tests such as urease activity and protein solubility in potassium hydroxide (KOH), which can be used to predict the degree of over or under processing of soybean meal.
Bakery by-product meal is also an important ingredient in livestock feeds and contains recycled baked goods unsuitable for human consumption. The nutritional composition of bakery by-product meal can be variable due to its composition (e.g., bread, snacks, and cookies). Therefore, it is important to monitor its nutritional content, particularly the level of sodium which, if underestimated, can lead to issues such as wet litter in poultry.
Animal by-product meals (e.g., poultry by-product meal, meat and bone meal) are a commonly used by-product of the rendering industry and are good sources of protein. The level of protein and minerals in these meals depends on their composition, such as the percentage of meat and bone. Proper handling of these meals is important to prevent microbial contamination during transportation and storage at the feed mill. Animal by-products may be restricted in diets to reduce the risk of disease transfer; for example, certain ruminant by-products cannot be used in ruminant feeds to prevent BSE based on FDA regulations, while other animal products such as porcine based products may not be added to swine diets to minimize the risk of PEDV.
Fats and oils are also important components of livestock diets and provide a more concentrated source of energy (2.25 times as much energy as carbohydrates) and essential fatty acids, particularly during periods of high energy demand such as lactation or during the hot season when feed intake is reduced. Fats and oils can increase feed palatability and reduce dustiness of the feed at the feed mill. However, proper storage and handling practices should be followed, and antioxidants may be added to reduce oxidation and rancidity and to maintain their nutritional quality. As discussed in other Feedstuffs articles, the inclusion of fats/oils in the mixer may be limited to around 0.5 to 1.0% to maintain pellet durability and the rest can be applied at the pellet die or after cooling (depending on the system) to maintain pellet quality and production capacity.
Calcium and phosphorus sources are also used in considerable amounts in feeds. Calcium sources include limestone, oyster shell, animal by-product meals, and dicalcium phosphate, among others. For poultry diets in particular, the particle size and the source of calcium are important as they influence its solubility. For instance, laying hens and broiler breeders can benefit from coarse/lower solubility calcium, which is absorbed at a lower rate. Coarse limestone particle size can help with eggshell formation and eggshell quality. Gulizia et al. (2023) evaluated the effect of calcium particle size and in-vitro solubility (Figure 1) and reported lower solubility of calcium sources with higher particle size. Attention should be paid to the level of magnesium in calcium sources, particularly when used in layers and broiler breeder diets, as it can lead to wet litter by reducing water reabsorption from the digesta.
Phosphorus sources include dicalcium, monocalcium, and defluorinated phosphate. Dr. Keith Behnke reported an improvement in pellet production rate of 23 and 33% when defluorinated phosphate was used to replace dicalcium phosphate and monocalcium phosphate, respectively. Since it is a harder rock, defluorinated phosphate likely increases pellet production rate by scouring or scrubbing the glass-like protein matrix that forms within the lumen of the pellet die.
To keep this article short, other ingredients won’t be discussed this time. However, readers are encouraged to understand other ingredients used at the feed mill. Remember, feed ingredients are the major cost in animal production and their physical and nutritional quality should be monitored on a regular basis to ensure good animal health and performance.
