Cattle feeding in Canada is based on grain.
One reason is that the cost per unit of energy is cheaper with grain than with other feed. It is also easier to store and handle than other feed and many consumers prefer the taste of grain-fed beef.
However, reliance on grain leads to cattle’s susceptibility to acidosis, one of the most common nutritional disorders in cattle.
Acidosis occurs when cattle eat grain that contains a large amount of carbohydrates. This results in the rapid production and absorption of organic acids as well as endotoxins in the rumen. It’s more likely to occur as animals are becoming accustomed to high grain rations.
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Acidosis is not just a drop in pH of rumen contents. It can also cause signs ranging from a minimal drop in feed intake to a disease so severe that it causes death. Other symptoms include founder, polioencephalomalacia, liver abscesses, bloat and clostridial infections.
Many cattle diagnosed as dying from sudden death syndrome die from acute acidosis. However, this cause of death is thought to be under-reported because of the time lag between death and necropsy.
Animals with acute acidosis may wander aimlessly in the pen, cannot stand or may appear to have brain damage.
Injections of thiamine often resolve the symptoms because thiamine production by the rumen microbes is impaired or the thiamine they produce is destroyed.
Thiamine deficiency is more of a concern in cattle that develop acidosis on transition rations. This disease rarely occurs when the cattle are on finishing rations containing 80 percent or more grain.
Acute acidosis triggers other problems.
The low pH damages the rumen lining, which causes poor nutrient absorption and reduces gains and lowers feed efficiency. These cattle become temporary or chronic poor doers.
A bout of acute acidosis can also lead to founder 40 to 60 days later.
Subacute acidosis occurs more frequently than the acute form, but it is much harder to recognize.
It drops feed intake and causes erratic feeding patterns, but because cattle are normally fed in pens of 100 head or more, identifying which ones are suffering from subacute acidosis based on reduced feed intake is almost impossible.
Daily observation of feed intake and its fluctuations may provide a clue.
Signs include panting, excessive salivation, kicking at the belly, eating dirt and diarrhea.
Researchers suggest that most animals have some degree of acidosis while in the feedlot, which means feedlot operators must miss many animals suffering from subacute acidosis. It is more common when there are changes in management or environment while cattle are on feed.
The focus must be on preventing subacute acidosis because it causes the most economic loss to feedlot operations. It starts with the choice of grain used in ration formulation.
Grain with the fastest rate of starch digestion is the worst. Wheat is digested the fastest, followed by barley. Whole corn and dry-rolled grain sorghum are the slowest. Thus, wheat and barley are the ones most likely to cause acidosis.
Overprocessing grain boosts performance, but it increases the possibility of acidosis because the carbohydrate is more readily fermentable.
Feeders will continue to use low roughage diets because it is difficult to manage roughage in the feedlot, but one solution is to add whole corn, high-moisture corn or alfalfa to boost roughage.
Adding alfalfa reduces feed efficiency and increases the cost of gain, but adding eight percent roughage can make the animals feel better and eat more, which results in a higher average daily gain and greater profitability.
Byproducts such as distillers grain are often generated by removing the starch from the grain. This seems to be the key in how they help control acidosis. More research is needed on these novel feedstuffs.
There is no one simple answer to eliminating acidosis because many factors affect its incidence. A fine line exists between optimal animal performance and creating acidosis, which makes them a challenge to balance.
Jeff Grognet is a veterinarian practising in Qualicum Beach, B.C.
