Beef producers often seek alternatives to traditional feed ingredients because of cost or availability. Use of byproduct feed ingredients can reduce costs or during periods of drought or forage shortages may mean the difference between maintaining the beef herd or selling out. In the feedlot, byproduct feeds can provide economical sources of protein and energy.

Cattle generally tolerate a wide variety of feed ingredients, and byproducts are generally useful when fed in low to moderate amounts. The most commonly available byproducts for beef rations include wet and dry corn gluten feed, wet and dry distillers grains, wheat midds, soybean hulls, wet and dry brewers grains, and corn hominy. Regional and even local coproducts abound in the industry, and their availability and cost dictate usage.

A great deal of research has been conducted to determine the usefulness of byproduct feeds for range and feedlot cattle. University and industry trials have demonstrated benefits for feeding wheat, corn, soybean, and brewery byproducts to beef cattle. While byproduct feeds can be excellent sources of protein, energy, and minerals, it is important to keep in mind the limitations for their use and the need for proper supplementation to maximize cattle performance.

Nutrient Composition of Byproducts
Table 1 provides typical byproduct analytical values. Since nutrient content can vary dramatically, it is important to analyze byproduct feeds for proper ration formulation and supplementation. The most important nutrients to consider are moisture, protein, calcium sulfur, and phosphorus. In some cases, it may be important to measure acid detergent fiber content to estimate feed energy value. In situations where heat damage is suspected, adjusted crude protein (equivalent to digestible protein) should be measured. The protein in distillers dried grains or brewers grains may be indigestible if excessive heating occurred during processing.

Supplementation
The versatility of byproducts leads to considerable variation in usage in beef operations. In nearly all situations, cost and availability of traditional protein and energy ingredients coupled with the availability and price of alternative byproducts dictate usage. The physical handling characteristics of some byproducts limit their feeding rates (e.g., wet brewers grains); whereas, nutrient concentrations or interactions with other feed ingredients or detrimental effects on rumen function or animal health will limit the use of certain byproducts. Also, environmental concerns have become more important, especially for feedlot operations. For example, the high concentration of phosphorus in corn byproducts may increase manure-handling costs or limit usage to ensure compliance with nutrient management legislation. While considerable usage variation exists, commonly used byproducts in beef diets can usually safely and economically be fed at 10% to 30% of diet dry matter.

For optimum performance, most rations containing byproducts will require some form of additional supplementation. The most important considerations are balancing protein needs, adjusting the ratio and amount of minerals supplied, and meeting vitamin requirements.

Protein
Protein supplementation strategies are becoming more sophisticated as researchers demonstrate benefits for balancing rumen degradable and rumen undegradable protein. However, for most situations, supplementing byproduct-containing rations to meet total protein requirement usually results in performance that meets producer expectations. Table 2 presents a list of special considerations for rations containing various byproduct ingredients.

Minerals

• Sulfur—Several coproducts contain more than 0.3% sulfur, which is the maximum recommended dietary concentration. If other dietary ingredients or water are high in sulfur, these levels can contribute to the incidence of polioencephalomalacia. There is some evidence that thiamin may be beneficial in reducing the symptoms of polio. Thiamin should be included in supplements for diets containing moderate to high levels of byproducts with elevated levels of sulfur.
   

• Phosphorus—Several byproducts contain more than 0.7%; whereas, the nutritional requirement is closer to 0.3% of diets on a dry matter basis. Excess phosphorus is seldom a nutritional problem and does not result in decreased animal performance. However, the excess phosphorus in manure and environmental considerations can increase the costs of manure disposal. Mineral supplements for diets with moderate to high levels of phosphorus should not contain any additional phosphorus

Corn Byproducts

• Corn Gluten Feed—Corn gluten feed is the portion of corn grain that remains after extraction of starch, gluten, and germ in the wet milling process. It is primarily bran, which is quite digestible in the rumen. Typically, corn gluten feed consists of about 2/3 corn bran and 1/3 corn steep liquor. Gluten feed has slightly lower energy value than corn, but gives similar performance when fed at low to moderate levels in feedlot rations. Dry gluten feed is a good cow feed because of its high phosphorus and potassium and low starch content. Dry and wet gluten feed are reasonably good sources of protein for brood cows and growing cattle. The protein found in gluten feed is mostly degraded in the rumen. Supplementing gluten feed diets with bypass protein, especially for lightweight growing cattle, provides some benefits. Since corn gluten feed is high in phosphorus, it is important to provide a high-calcium mineral supplement to balance the Ca:P ratio. Supplementing diets with thiamine may be beneficial due to the increased tendency for polio-like symptoms in feedlot cattle fed high amounts of gluten.
   

• Corn Distillers Grains—Distillers grains are byproducts of the dry milling of corn grain for alcohol production. The amount of solubles added back to the solids remaining after distillation varies by dry milling plant and dictates whether wet or dry distillers byproduct is produced. Distillers grains usually contain some solubles. During fermentation to produce alcohol, nearly all of the corn starch is removed and the remaining protein, fat, and fiber are concentrated about three-fold. Distillers grains are very palatable and are an excellent energy feed for cattle. The high bypass protein content of distillers grains is beneficial for growing cattle. Distillers grains may be useful in feedlot arrival rations provided total fat content of the diet is within NRC guidelines. The bypass protein of distillers is low in lysine and, if bypass protein supplementation is desired, high-lysine ingredients should be considered (e.g. bypass soybean meal products). Providing supplemental rumen degradable protein (e.g., urea, biuret, SBM) may yield some benefits due to the high bypass protein content of distillers grains. Dried distillers grains can vary considerably in color because of variable heat processing, and dark DDG may have more indigestible protein due to heat damage.
   

• Corn Hominy—Hominy is the byproduct of the processing of corn meal for human consumption. It is a mixture of corn bran, corn germ, and a portion of the starch. Hominy is higher in energy, protein, fat, and fiber than corn grain. Since fat content of hominy may range between 5 to 12%, care should be taken to ensure total ration fat is not excessive when using hominy. The high starch and relatively low protein content make hominy a poor feed ingredient for cattle consuming high-roughage rations. The best fit for hominy is as a corn replacement in feedlot growing and finishing rations. Feeding levels of 10 to 15% of ration dry matter are common. Protein supplementation will be needed to balance the high energy content of hominy.

Soybean Byproducts
Soybean Hulls—Soyhulls are the outer seedcoat of the soybean seed that have been removed by aspiration after beans are cracked for oil extraction. Hulls are normally toasted and ground before being added to low-protein soybean meal or being shipped for animal use. Soyhulls contain a moderate amount of protein and are high in digestible fiber. They are very palatable and are an excellent feed ingredient for both forage- and grain-based rations. Soyhulls are most effective when limited to about 30% of the total ration and are probably not ideal as a roughage source in feedlot finishing rations because of their dust and low effective fiber value (scratch). Feeding high levels of soyhulls can lead to bloat and loose stools especially in feedlot situations. Rations containing soyhulls will usually require additional protein supplementation.

Brewery Byproducts
Brewers Grains—The spent grain and hops from the brewing industry is marketed to the cattle industry as wet or dried brewers grains. Barley is the most common starting grain although some breweries may use corn, rice, and wheat. In addition to the spent grains, the residual yeast cells are dried and fed as value-added brewers yeast culture. The high moisture content of wet brewers grains (70 to 80% water) typically restricts usage to a limited distance from the brewery and to larger operations that can successfully manage storage and handling. Brewers grains are reasonably palatable and a good source of bypass protein for growing cattle. Rations should be balanced based on brewers grains’ high phosphorus and sulfur content and deficiency of calcium and potassium.

Wheat Byproducts
Wheat Middlings—Wheat midds are a byproduct of flour milling. The composition varies depending on the amounts of bran, germ, and starch added to the midd. The protein and energy in midds are readily utilized by ruminants, with rumen digestion of protein and fiber being quite high. In growing cattle diets, midds have an energy value similar to corn. When fed in moderate amounts (e.g., 5 to 6 lb/head/day), they are acceptable for brood cows diets because of their protein content and protein degradability and their high phosphorus and potassium content. Feeding higher levels of midds may cause digestive upsets and impair fiber digestion due to starch content. Diets containing significant amounts of midds will require protein supplementation and special consideration for calcium fortification.

Conclusion
Byproduct feed ingredients can provide an economical alternative to traditional grains and forages used in beef cattle operations. Animal performance can be maintained or even improved if byproducts are used within nutrition and feed management guidelines. It is important to analyze byproducts for nutrient content and to recognize the challenges associated with byproduct storage and management. Supplementation with protein, minerals, and vitamins is a key strategy for improving the performance of cattle fed rations containing byproduct feed ingredients. Use of supplements formulated to fit the nutritional characteristics of the byproduct will increase the value of the byproduct and lead to better economic returns.

 Table 1 Typical Composition of Byproduct Feed Ingredients*

Nutrient	Wet Corn Gluten Feed	Dry Corn Gluten Feed	Soybean Hulls	Wheat Middlings	Wet Distillers Grains	Dry Distillers Grains + Solubles	Wet Brewers Grains	Dry Brewers Grains	Corn Hominy
Dry Matter	45	90	91	89	25	91	21	92	90
Protein, % of DM	21	23.8	12.2	18.4	29.7	29.5	26	29.2	11.5
RUP, % of Protein	25	25	42	26	55	73	59	66	52
RDP, % of Protein	75	75	58	74	45	27	41	34	48
SIP, % of Protein	50	50	18	40	25	19	8	4	18
NEg, Mcal/cwt	62	62	42	64	52	51	37	35	69
NEm, Mcal/cwt	92	92	59	95	74	72	61	58	87
ADF, % of DM	11.1	16	50	11.1	18	18	22	24	13
NDF, % of DM	45	36.2	66.3	35	40	46	42	48.7	23
TDN, % of DM	82	83	80	85	90	88	70	67	91
NFC, % of DM	27	29	14	41	16	9	15	7	57
Fat, % of DM	3.6	3.9	2.1	3.2	9.9	10.3	6.5	10.8	7.3
Fiber, % of DM	8.4	8.4	39.6	8.4	9.9	9.9	17.5	17.4	6.2
Calcium, % of DM	0.1	0.07	0.53	0.15	0.32	0.32	0.29	0.29	0.05
Phosphorus, % of DM	1	0.95	0.18	1	1.4	0.83	0.7	0.7	0.57
Ca:P Ratio	0.1	0.07	2.94	0.15	0.23	0.24	0.41	0.41	0.09
Ash, % of DM	3.5	6.9	4.9	2.4	4	5	10	4	1
Potassium, % of DM	1.5	1.4	1.29	1.1	1.83	1.07	0.58	0.58	0.65
Sulfur, % of DM	0.3	0.47	0.11	0.19	0.4	0.4	0.34	0.4	0.03
Magnesium, % of DM	0.5	0.4	0.22	0.38	0.65	0.33