TAKE CAREFUL CONSIDERATION BEFORE FEEDING BY-PRODUCTS

by: Stephen B. Blezinger
Ph.D., PAS

Part 2

In Part 1 of this series we began a discussion on feeding by-products to cattle. We started with the class of by-products that are some of the oldest and probably most well known – cotton products – those derived from the cotton industry and include materials such as cottonseed meal, whole cottonseed, cottonseed hulls. While these are the most common by-products in the cotton family other associated products include cotton gin trash and gin motes. Gin trash includes leaves, stems and some lint that is extracted during the ginning process from the picked cotton. Another by-product of the gin is motes. Motes are small, immature seeds with attached fiber that are removed at a different stage of the gin stand than the mature seeds. These can also be fed to cattle.

As mentioned, cotton by-products are a broad and widely used class of materials in the cattle feeding and supplementation industry. But they are really just the tip of the iceberg. As the Ag industry moves forward and research and development finds uses for the different products we produce that does NOT include feeding to livestock, the value of the basic grains increases. Products like corn, soybeans and so on can be processed to produce a wide variety of products for industrial as well as human food usage. As this trend continues we are already beginning to see an increase in the use of by-products since as the value of the basic grains increases and the availability of the by-products increases, by-products become a better value per unit of nutrient (protein, energy, etc.) and thus their use makes better economic sense. Many experts believe that the day will come when we will no longer be able to feed basic grains to cattle and that the only thing we will feed will be by-products. As an aside, by-products are also referred to as co-products since they are produced at the same time that the materials the basic grain is being processed for is produced.

As we discussed in the last issue there is a lot of nutritional value to be extracted from the different by-products but there are also issues that have to be taken into consideration. Every by-product has its own set of idiosyncrasies that must be accounted for when fed to cattle. We'll start off this series by discussing feeding of corn by-products, another of the most common by-products out there, especially with the development and growth of the ethanol industry.

Corn By-Products

Dr. Rick Rasby (University of Nebraska) recently discussed the value of corn by-products. He pointed out that corn byproducts can be used as either a protein or energy supplement for backgrounding growing cattle, replacement heifers and cow diets. The energy value of distiller's grains is greater than that of corn. The protein content is three times that of corn and distiller's grain is a good source of by-pass protein (protein that is not degraded in the rumen). And, distiller's grains are a good source of phosphorus. When distiller's grains are fed in high forage diets, there is no negative relationship between distiller's grain and forage because most of the starch has been removed to produce ethanol. This also greatly reduces the potential incidence of acidosis or bloat. Thus, corn co-products appear to be a good fit as a protein or energy supplement in cow feeding programs based mostly on forage.

There has been a huge amount of research on feeding distiller's grains (wet and dry) to cattle. It was obvious that as the ethanol industry ramped up their production that a lot of distiller's would also be produced and that the ethanol plant would have to move these by-products steadily in order to prevent a huge accumulation. Given the predominant presence of ethanol plants in the Midwest corn growing areas, the obvious choice is feeding these by-products to cattle. Research has gone into their inclusion in swine and poultry diets but cattle feeds appear to provide the best fit. Below are details of a couple of studies conducted at the University of Nebraska. Distillers grains were included in the cattle diets to supplement energy, protein, or both energy and protein to mostly forage diets.

The first was a two-year study (Martin et al. 2007 Nebraska Beef Report) which evaluated feeding dried distillers grains plus solubles (DDGS) during heifer development on growth and reproductive performance. Supplements for both DDGS fed heifers and control heifers provided similar amounts of crude protein, energy, fat, and fatty acids. Heifer pubertal development and overall pregnancy rate were not affected between control and DDGS fed heifers. However, AI conception rate and AI pregnancy rate were improved by feeding DDGS in the heifer development diet. The replacement heifers in this study were supplemented at 0.58 percent of their body weight on a dry matter basis thus if the average weight of the heifers was 600 pounds, then the group was fed 3.5 pounds per head per day on a dry matter basis (a little over four pounds as-fed). Limestone (40 pounds of limestone per ton) was mixed with the DDGS to add calcium to the diet. Heifers in this experiment did not experience sulfur toxicity. The heifers were projected to gain 1.5 lb/day and their actual gain was 1.35 lb/day. This experiment demonstrates that distillers grains, fed at 0.58 percent of body weight dry matter basis, does not have a negative impact on reproductive performance in replacement heifer diets.

As beef cow producers continue to search for management practices to reduce costs, including heifer development costs, there appear to be opportunities to develop heifers using crop residues and distillers grains. Distiller's grains have a high energy and high protein content. In addition, distillers grains fit well as a protein and (or) energy supplement in many grazing situations. Beef producers often target a specific ADG when growing calves. DDGS were fed to weanling steer calves grazing non-irrigated corn residue to determine daily gain response and residue intake response to increasing levels of DDGS (from 1.5 to 6.5 lb/day in 1 lb increments; Gustad et al., 2006). Daily gain increased from 0.9 (1.5 lb DDGS) to 1.8 (6.5 lb DDGS) lb/day. These results provide information for selecting a DDGS supplementation level to achieve a target gain when calves are grazing corn residue. Although this experiment used steer calves, there is direct application to developing replacement heifers. This study suggest that calves can “program feed” to a specific ADG based on the amount of distillers grains supplemented while grazing corn stalk residue.

A second experiment was conducted using cornstalk residue and supplementation as part of the development program for replacement heifers (Larson et al., 2010 Nebraska Beef Report). While grazing corn residue heifers were supplemented with 2.5 lbs of a 28 percent crude protein cube. Yearling pregnancy rate varied between 84 percent and 92 percent and subsequent pregnancy rate as 2-year-olds of these same females ranged between 77 percent and 100 percent. The data suggests when heifers were supplemented at the higher rate, reproductive performance was numerically greater. A producer could consider, when it can be economical, using DDGS as the supplement because it is a good protein and energy source.

Spring-calving heifers in mid-gestation grazing residue fields the first 25 days should meet both their protein and energy needs and should gain weight and body condition, especially if some corn is available. After the grain has been consumed, protein and energy supplementation appear to be needed. The remaining corn residue is between 53 to 54 percent TDN and crude protein during this time period will be about 5.3 percent CP. For a 1,000 pound heifer in mid-gestation and average body condition, energy and protein in the diet are deficient when only on corn stalks (same as with grass hay). These heifers are approximately 0.60 to 0.70 pounds deficient in crude protein and 0.7 lb to 0.9 deficient in energy. Because distiller's grains are excellent protein and energy source and because there is a calculated deficiency in both protein and energy, it appears to be a good fit and should correct these deficiencies.

Another corn by-product that can be used as a protein and energy supplement is corn gluten feed. Corn gluten feed is a byproduct of the wet milling process. Wet milling separates the corn kernel into starch, oil, protein, and bran. Corn gluten feed is not to be confused with corn gluten meal. Corn gluten meal has two times the protein content of corn gluten feed. Also the protein in corn gluten feed is degraded relatively rapidly in the rumen versus the protein of corn gluten meal is degraded relatively slowly (more by-pass potential). Like DDG, corn gluten feed is available in wet and dry forms in some areas.

Corn gluten feed, after processing, starts in a wet form. Wet corn gluten feed has some nutritional advantages over dry corn gluten feed but the dry product is easier to handle. Wet corn gluten feed has a bunk life of a few days in summer and one to two weeks in winter. Because of bunk life and transportation costs, wet corn gluten feed is only an option to producers that are in relative close proximity of the milling plant.

Crude protein values have ranged from 17 percent to 26 percent and fat content has ranges from 1 to 7 percent. Therefore, regular feed testing is recommended or buying corn gluten feed that has a guaranteed analysis. This is true of most by-product feeds.

The concentration of crude protein is about as twice as high in corn gluten feed as it is in corn grain. Corn gluten feed is low in calcium but has significant amounts of phosphorus. The calcium to phosphorus ratio is about 1:10. The desired ratio of feeding cattle is a minimum of 1.5-2 to 1 calcium to phosphorus. Therefore, corn gluten feed fed at high levels without calcium supplementation could result in urinary calculi problems. It is necessary to feed calcium levels above NRC minimum requirements if more than 1/3 of the diet is corn gluten feed. Trace mineral and vitamin levels can vary greatly from batch to batch.

Considerations

As mentioned before, there are no perfect feed ingredients. Both DDGs and corn gluten feed have limitations that need to be recognized. A few are listed here:

1) Variation – like all by-products there is variation in these two ingredients, in many cases from load to load. There can be a significant swing in nutrients such as protein, fat, energy, mineral content. The producer needs to be aware of this factor and have some margin for error built into his feeding program. Regular testing is advised.

2) Availability – while this is not as significant for these two products as for some others there can be situations in some areas where availability can become a problem. This becomes true when markets for conventional grains are high and the demand for these by-products also becomes high. It is important that the producer anticipates what needs he has and that he communicates with his suppliers to prevent running short.

3) Palatability – introducing either DDG or CGF needs to be done carefully in order to give cattle time to adapt to the taste and smell.

4) Mineral content – again, there is some variation here. One of the biggest concerns is the sulfur content in both of these by-products which can run fairly high. High sulfur can create problems with intake as well as other metabolic issues (including sulfur toxicity and contributions to polioencephalomacia). It is important to keep total sulfur in the animal's diet below .4% on a dry matter basis. Sulfur is also well known to reduce the absorption (antagonize) of copper. This can begin occurring at levels as low as .25 percent sulfur in the diet. It is very important to be aware of the sulfur content in the supply of these by-product purchased to feed at levels to prevent the intake of excessive sulfur.

5) High fat (in DDGs) – DDG can run high in fat (8-10 percent or more). While fat is an excellent energy source, excessive fat intake (above 6-7 percent in the total diet) can depress fiber digestion in cattle diets. Again, this simply indicates that care needs to be taken to not feed excessive levels of these by-products.

6) Shelf-life – the wet versions of both by-products have a limited shelf life and must be fed within a short amount of time. In some cases within five to seven days of receiving the load.

Conclusions

Like many by-products, DDG and CGF can be excellent sources of nutrients for cattle and have a place in many feeding programs. They need to be balanced into the feed or ration carefully and consideration given to the limitations. In the next part of this series we will continue this discussion on by-product use and considerations.

Dr. Steve Blezinger is and nutritional and management consultant with an office in Sulphur Springs Texas. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at (903) 352-3475 or by e-mail at sblez@verizon.net.







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