More Distillers Grains in Cow Diets Possible

By Jane Fyksen, Crops Editor
Thursday, June 15, 2006 12:12 PM CDT

With more ethanol plants dotting America's Dairyland every year, the current generous supply and competitive prices for distillers grains make it economically attractive for dairy producers to feed as much of this byproduct feed as possible.

David Schingoethe, dairy scientist at South Dakota State University, says it's easy to formulate balanced diets for lactating cows that contain about 20 percent of the ration dry matter as distillers grains - more than the conservative amounts sometimes recommended, but still less than the 30 to 40 percent fed in some dairy research trials or the 40 to 50 percent frequently included in finishing cattle diets.

Schingoethe explores feeding distillers grains - especially larger amounts - to dairy cattle, pointing to where "the maximums may occur." He also looks at possible differences to consider when feeding wet versus dried distillers grains.

He says products available from the ethanol industry today contain more protein and energy than older "book values" - even those listed by the National Research Council (NRC) feeding guidelines. They can be of "uniformly good quality," too, reflecting improved fermentation efficiency of the new-generation ethanol plants, he adds.

Distillers grains is a very good protein source (over 30 percent CP). It's high in ruminally undegradable protein (RUP). It's a very good energy source for lactating cows and growing cattle (with about 1.2 Mcals per pound of DM). The modest fat concentration (10 to 12 percent of DM) and the readily digestible fiber (39 percent neutral detergent fiber or NDF) contribute to the high energy in distillers grains.

For several years now, Schingoethe and others have recommended feeding 20 percent of ration DM as distillers. "This may be considered a sizable amount - approximately 10 to 13 pounds per head per day of dried or 30 to 40 pounds per day of wet distillers grains - but an amount that can be easily fed in nutritionally balanced diets and with very good animal performance," he maintains.

He bases his recommendation on research at South Dakota State University and elsewhere. He contends his "20 percent of DM" limit "may actually be conservative."

Virtually all distillers available today is "with solubles" (DGS), because the solubles are usually blended back in. "In fact, many research studies don't designate whether the product used was with or without solubles," says Schingoethe. "The composition of corn distillers grains is essentially the same with or without solubles added, except for a lower phosphorus content (about 0.4 percent) without solubles, because the solubles are quite high (about 1.35 percent) in phosphorus." He adds that the protein content may be slightly lower and the fat slightly higher with solubles, reflecting the slightly lower protein and higher fat content of solubles.

He notes if a DGS product contains substantially more fat (over 15 percent) and/or phosphorus (over 1 percent), it's very likely more-than-normal amounts of solubles were blended with the distillers, or that the processor had problems with materials separating during the handling of solubles.

Such variations also point out the importance of obtaining data on the specific product you're receiving, and the importance of suppliers providing uniform, standardized products.

This specialist says that down the road, there'll be a host of new and improved products. Already, improvements in fermentation technology provide DDGS today that contain more protein and energy than previously. It's also becoming feasible to "fractionate" DGS into products higher in protein, other products higher in fat or in fiber and products higher or lower in phosphorus.

How production responds

Schingoethe says distillers grain is palatable and readily consumed by cows whether it's wet or dried. However, some decreases in DM intake can occur when cows are fed high amounts of DGS, especially wet DGS.

TABLE MENTIONED make sure on same page

Table 1 summarizes virtually all research available about feeding DGS to lactating cows. Anywhere from 4.2 percent of total dietary DM to 41.6 percent was fed in 24 studies from 1982 to 2005.

He says DM intakes were as high or higher than intakes of control diets - even with more than 20 percent DGS in the diet.

While intakes weren't affected even by high amounts of dried DGS, with wet DGS diets, intakes tended to decrease when more than 20 percent of the DM was wet DGS. Intakes significantly decreased when more than 30 percent of ration DM was wet DGS.

"Gut fill may limit DM intake when diets contain less than 50 percent DM, which is likely to occur when diets contain more than 20 percent of DM as wet DGS - in diets that already contain other moist feeds, such as corn silage or haylage," says Schingoethe.

One recent study saw decreased DM intake - and a corresponding drop in milk production - when wet DGS supplied more than 30 percent of the dietary DM in diets that contained only 40 to 46 percent DM. In his own research, Schingoethe observed decreased DM intake when diets contained 31 percent of DM as wet DGS in a 47 percent DM diet. But milk production was similar to the control diet.

In all the studies, milk output is usually similar to control diet production - and in many cases higher when any amount of DGS is fed. Control diets typically fed soybean meal.

With dried DGS, production tends to be highest for diets containing up to 30 percent DGS. With wet DGS, production is highest when cows are fed up to 20 percent DGS.

Schingoethe highlights the importance of protein quality. In one study, when a dried DGS product was darker and possibly heat damaged, production was lower than when a lighter, golden- colored dried DGS was fed, but milk output was still similar to production achieved with soybean meal.

That said, he says the quality of protein in corn DGS is fairly good today. "As with most corn products, lysine is the first limiting amino acid in corn DGS for lactating cows," he notes. "But corn DGS is a very good source of methionine." Sometimes, but not always, milk increases when cows were fed supplemental ruminally protected lysine and methionine with dried DGS, or when dried DGS was blended with other protein supplements containing more lysine.

A study this year reveals that while there may be differences in protein quality in various sources of dried DGS, milk yield and milk protein differences may be slight - unless a product is really heat-damaged. In this study, dried DGS supplied 20 percent of ration DM.

Feed efficiency, says Schingoethe of DGS, is comparable or higher even than cows on control diets. A beef study points to fewer off-feed problems and less subacute acidosis. He says that even though DGS contains similar amounts or more energy even than corn, the energy in DGS is primarily in the form of digestible fiber and fat. In corn, most of the energy is starch. Ruminal starch fermentation is more likely to result in acidosis, laminitis and fatty liver.

Schingoethe's institution has a study going now in which lactating cows are being fed 15 percent of dietary DM as wet DGS for the entire lactation, during their dry period and the first 70 days of the next lactation. So far, in the first year, they're seeing similar milk production and composition, feed intake and reproductive efficiency with wet DGS as with the control diet.

Wet versus dry

There hasn't been much work done directly comparing diets with wet versus dry DGS. One recent study showed a "tendency" for more production from wet DGS instead of dried and a "tendency" for more production at 20 percent of ration DM as DGS versus 10 percent - either wet or dried.

Digestibility is usually considered to be similar. Again, though, there are few studies directly comparing the two types.

The main considerations with wet versus dried DGS are handling and cost. Dried can be stored longer, shipped farther and easily blended with other ration ingredients. Wet DGS doesn't stay fresh and palatable for extended periods - especially in the summer. About a week is the norm, though in the winter, it'll stay palatable for three weeks. Adding propionic acid or other organic acids to extend the shelf life of wet DGS is possible.

Schingoethe has successfully stored wet DGS for more than six months in silo bags - alone or blended with soy hulls, with corn silage and with beet pulp. Field reports indicate successful preservation of wet DGS for over a year in silo bags.

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