Distillers grains are a byproduct of whiskey and fuel ethanol production
The crude protein fraction of distillers grain (being a byproduct of corn) is relatively undegradable in the rumen of cows.
This is especially true of dried distillers grains with solubles as the product has been reheated and dried, thus altering the protein fraction making it less available in the rumen.
According to the analyses of the National Research Council and others , increasing rumen undegraded protein has a linearly increasing effect on milk and milk protein production when added to diets low in rumen undegraded protein .
This result has been confirmed for rumen undegraded protein derived from distillers grain when rumen degradable protein was provided at a constant concentration. In this and in an additional experiment when rumen undegraded protein was provided as distillers grain instead of soybean-based protein, milk and milk protein production were greater for cows fed distillers grain-based rumen undegraded protein.
Quality of the crude protein in distillers grain is proposed to be limited by the amino acid lysine. When dried distillers grains with solubles was included at 15% of dry matter with corn silage, alfalfa hay, or an equal mixture of both comprising 50% of dry matter, milk production was increased with increasing levels of alfalfa in the forage component. Lysine was found to be the first-limiting amino acid for mammary gland extraction efficiency for the corn silage and the corn silage/alfalfa hay diets, whereas methionine was first-limiting for the alfalfa hay diet. It has been speculated that high corn silage diets may benefit from supplemental bypass lysine, although responses to date have been inconsistent when lysine and methionine were supplemented in diets containing alfalfa hay as a component of the forage
Energy
Although distillers grain is typically fed as a source of crude protein, the energy concentration of distillers grain is equal to or greater than the concentration of corn. However, rather than coming from starch, the energy in Distillers Grain is provided by fat, digestible fiber, and crude protein. This may positively affect the rumen environment and reduce the incidence of acidosis, as is commonly observed in beef cattle.
Neutral Detergent Fibre
The primary carbohydrate fraction in distillers grain is neutral detergent fibre. Feeding high levels of distillers grain will increase the concentration of neutral detergent fibre in the diet. Several experiments have shown that the distillers grain is comparable to forage as a source of effective fiber. These experiments have only fed up to 15% of dry matter as distillers grain. Due to particle size considerations it is likely that with higher levels of distillers grain inclusion, the ability of distillers grain to replace the effective fiber of forages will be limited.
An opportunity may exist to replace a portion of the corn and protein supplement with distillers grain, and this is what most experiments have tested. Although the Neutral detergent fibre concentration of these diets will be greater than diets containing corn, as discussed later, milk production is equal to or greater than diets containing distillers grain
Fat
High levels of fat are present in distillers grain Rations must be balanced to keep dietary levels of fat less than 5% of ration dry matter (excluding bypass fat) to avoid inhibiting rumen function.
Variability in fat levels can be problematic with dried distillers grains with solubles and must be controlled for normal rumen function. If other feed sources containing fat (whole cottonseeds or soybeans) are used in the ration, the amount of distillers grain that can be fed may be limited.
Phosphorus and Sulphur
Nutrient management plans are often designed around the excretion of nitrogen and phosphorus. The phosphorus concentration of distillers grain is high relative to the requirement of the cow.
The availability of phosphorus appears to be greater in distillers grain than in corn, possibly due to the hydrolysis of phytate-phosphorus during fermentation. Given this, it has been suggested that supplementation of inorganic phosphorus may be reduced or eliminated with a diet containing adequate levels of The level of phosphorus must be monitored in the final ration to meet nutrient management objectives. Typically dried distillers grains with solubles has two times the phosphorus levels found in whole corn. High levels of dried distillers grains with solubles feeding may increase phosphorus excretion by the herd.
Levels of sulphur are high and variable in distillers grain It is typically recommended that ruminant diets contain less than 0.3% of dry matter as sulphur. Diets are often formulated for higher concentrations of sulfur (especially when feeding anionic salts) without apparent problems. It is important to test and monitor the level of sulfur present in the final ration. In general Dried distillers grains with solubles has four times the sulfur of whole corn, which must be taken into account when balancing rations.
Maximal Level of Distillers Grains
The typically recommended maximum level of distillers grain for dairy cattle is 20% of dietary dry matter. However, it is often recommended to limit the feeding level to 10 to 15% due to the other attributes and components of dried distillers grains with solubles
Dairy Cows were fed diets of dried distillers grains with solubles or wet distillers grains with solubles at 0, 10, or 20% of dry matter, where corn and soybean meal were replaced by distillers grain While dry matter intake tended to be lower for cows consuming distillers grain milk, protein, and fat yield were greater for cows consuming diets containing distillers grain.
This resulted in improved efficiency of feed conversion (feed efficiency) for cows fed diets containing distillers grain Intake and production were not affected by level of distillers grain inclusion, although numerical differences in the responses led to a tendency for increased feed efficiency for cows consuming 20% versus 10% distillers grain fed diets containing 0, 10, 20, and 30% Dried distillers grains with solubles or 0 and 30% dried distillers grains with solubles in two experiments and evaluated productive responses. In these experiments,dried distillers grains with solubles replaced both forages and concentrates.
In the first experiment, dry matter intake and milk production increased with increasing inclusion of dried distillers grains with solubles without affecting feed efficiency. In the second experiment, dry matter intake was increased for cows fed dried distillers grains with solubles diet but milk production and feed efficiency were unaffected.
Finally, it may be important to monitor the levels of mycotoxins in distillers grain especially during drought years. Like the nutrients that are present in corn fermented for ethanol, the concentration of mycotoxins can also be increased if present on the corn. Mycotoxins can contaminate distillers grain and reduce animal performance and can also be transferred to milk if present at high levels.
Considering the information provided here, it appears that the maximum inclusion level for lactating dairy cow diets is limited by the resulting nutrient composition of the entire ration. Therefore, rations must be evaluated to provide an appropriate intake of energy, rumen degradable and undegradable protein, and phosphorus to meet production and nutrient management goals.
While some nutritionists will recommend higher levels and can have success with these high levels, at present we do not recommend more than 10 to 15% inclusion in a lactating dairy cow diet. We do not recommend going above this level unless you are paying close attention to the nutrient content of the dried distillers grains with solubles product being fed, as well as the herd ration and cow performance. Fat level of the dried distillers grains with solubles protein quality feed variability, phosphorus and sulfur levels are all concerns that must be accounted for when using this feed source at levels above 10 to 15%.
Conclusion
Feeding distillers grain to dairy cows is a viable option for dairy farmers to provide supplemental rumen undegradable protein and energy to dairy cows, with equal or improved milk production. As with forages and many other by product or commodity feeds, having frequent and accurate nutrient analyses for distillers grain is important for ration balancing and nutrient management. When feeding distillers grain to dairy cows, nutritionists and producers must pay close attention to dietary crude protein and rumen degradable protein, phosphorus and sulphur, and fat concentrations to obtain optimum rumen function, cow productivity, and nutrient excretion.
