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Acidosis Still A Concern When Feeding Ddgs

You shouldn’t assume DDGS is a feed stuff that will aid in buffering the rumen of cattle fed high-grain diets

The ethanol fuel production process converts grain starch to alcohol and leaves behind a co-product— dried distillers grain with solubles (DDGS) — that is virtually void of starch, but rich in protein, fat and digestible fibre that combine to provide an excellent source of energy and protein in cattle diets.

The rapid digestion of grain starch in the rumen of feedlot and dairy cattle is associated with digestive disorders, such as acidosis and bloat. Therefore, the premise has always been that, by their nature, DDGS should help reduce the likelihood of digestive disorders in cattle and not predispose them to acidosis, says John McKinnon, beef chair with the department of poultry and animal science at the University of Saskatchewan (U of S).

As producers gain experience feeding wheat-based DDGS and researchers continue to explore their feeding value, it is becoming apparent that substituting DDGS for grain at high levels in finishing rations doesn’t mitigate digestive upsets to the degree expected given their nutrient makeup.

“Producer experience with feeding DDGS is that they are very palatable to cattle and stimulate intake. However, in contrast to expectations, feeding DDGS does not appear to reduce potential problems with sub-acute acidosis, particularly when rumen pH is used as an indicator,” McKinnon comments.

Swings in ruminal pH from normal (6.5 to 7.0) to acidic (5.5 and lower) have traditionally been associated with high levels of starch from grain-based diets undergoing rapid digestion in the rumen. Under such conditions, the production and concentration of organic acids in the rumen increases, including that of lactic acid. The rumen has mechanisms to stabilize or buffer this increase in rumen acidity. Over time on high-grain diets, or when hungry or unadapted animals consume a large amount of highly digestible carbohydrates (grain), the rumen’s ability to withstand the effects of the acids decreases and ultimately rumen pH falls. A consequence of this type of change in rumen pH is the development of acidosis which can range in severity from acute to sub-acute. Acute acidosis can lead to the death of the animal if untreated. Sub-acute acidosis is associated with reduced feed intake and poor feedlot performance. Over time, chronic cases of sub-acute acidosis can lead to further disease problems including liver and lung abscesses and lameness.

“Our research has shown that, despite the low-starch nature of wheat-based DDGS, rumen buffering is not stimulated by feeding this byproduct,” says McKinnon. This may be due to its small particle size (and thus low effective fibre content), or due to its acidic nature resulting from ethanol production practices.

Though there isn’t a rumen buffering effect, DDGS fed at appropriate levels in the diet result in the same or better animal performance as barley grain, he says.

Research recently published in the Canadian Journal of Animal Science (Vol. 88, 2008) is now available from the University of Saskatchewan and Agriculture and Agri-Food Canada at Lethbridge showing the feeding value of DDGS and confirming producers’ observations.

At the U of S, wheat-based DDGS was fed in backgrounding diets at 25 and 50 per cent of the diet dry matter as a replacement for barley grain. There was no difference in dry matter intake, however, cattle consuming DDGS had the best gains. As a result they were 8.7 per cent more efficient on average than cattle fed the barley grain control diet. Animal performance was optimized at the 25 per cent inclusion level, McKinnon explains.

A second U of S study found no adverse effects on daily gain, feed intake, efficiency or carcass quality when wheat-based DDGS was fed in finishing diets at levels up to 23 per cent of the diet dry matter.

Work at Lethbridge showed similar results in that when DDGS was fed at 20 per cent of the dry matter of a finishing diet, there was no negative impact on gain, feed intake, or carcass quality. When the percentage of DDGS in the finishing diet was increased to 40, then to 60 per cent, the cattle had to eat more of the total ration to get the same gain. As a result, feed efficiency declined as DDGS inclusion levels increased. This work also showed that DDGS fed at 60 per cent of the diet dry matter, reduced the dry matter digestibility of the diet, McKinnon adds.

In summary, research to date identifies that wheat-based DDGS can be fed at levels up to 40 to 50 per cent of the ration dry matter in backgrounding diets without any adverse effects, with the optimal level in terms of animal performance at 25 per cent of the ration dry matter. The optimal inclusion rate in finishing diets is 20 to 25 per cent of the dry matter.

“However, if you are relying on DDGS as part of a feeding system, you shouldn’t assume DDGS is a feed stuff that will aid in buffering the rumen of cattle fed high-grain diets. Proper bunk management and step-up feeding programs are still critical to moving cattle on to higher energy diets,” McKinnon stresses.

As with feeding any type of byproduct, he encourages producers to consult with a qualified nutritionist when developing feeding programs based on DDGS, particularly from the point of view of the high nitrogen and sulphur content, which can negatively impact animal health and performance if not managed properly.

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