The far-reaching effects of rumen acidosis

It is a painful condition caused by eating too much highly digestible starch or sugar and can also decrease performance

Ruminal acidosis can be a painful condition for cattle and could lead to other problems like ruminitis, laminitis or liver abscesses.

Acute acidosis can occur when cattle consume too much highly digestible starch or sugar.

It is often seen among feedlot cattle but it can also affect the cow-calf sector.

It is an animal welfare concern and it decreases performance with a small weight loss, said Greg Penner of the University of Saskatchewan.

“Our dietary management has been designed to promote a reasonable level of dry matter intake with a highly fermentable diet to maximize ruminal fermentation,” he said at the annual Animal Nutrition Conference of Canada in Edmonton.

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“The challenge comes when we drive intake and fermentation to the point the animal cannot cope,” he said.

Ruminants are able to digest forages with the help of rumen microbes. Each has a preferred food source and all break down simple sugars into volatile fatty acids.

These fatty acids are absorbed through the rumen wall into the bloodstream and provide energy to the cattle.

Finishing beef cattle are fed highly fermentable grain diets that can increase the rate and extent of fermentation within the rumen and consequently, the rate of acid production.

Too much acid reduces rumen pH levels that can compromise the ruminal and intestinal walls. There is a reduction in the absorptive capacity of nutrients and a potential reduction in feed intake as well as an increase in liver abscesses.

When rumen pH levels drop too far, fibre digestion decreases, nutrient absorption is reduced and the lining of the rumen and intestines may be damaged.

Feeding ionophores helps to reduce acidosis by inhibiting the growth of major acid-producing bacteria.

Some of Penner’s research examined what happens to cattle when they move from a backgrounding diet to a highly concentrated grain diet.

A study at a commercial feedlot examined the transition where cattle went from a diet of 40 per cent forage to less than 10 per cent forage.

“As the dietary concentrate is increased there is a change in pH from 6.1 to 6.2 and it dropped on the finishing diet. Overall, severity is relatively low, but we do see increases in deviation,” he said.

As cattle progressed through the finishing phase, researchers noted an increased severity of low rumen pH where it was a level of 5.5 for more than three hours a day.

The conventional thinking is once adapted to a particular diet, cattle should be able to tolerate more concentrates, but his research team saw a continuing decline in rumen pH.

They found cattle could recover from acidosis, but were always susceptible to future bouts.

“Response to subsequent bouts of acidosis tend to be increased by previous events of acidosis,” he said.

Environmental factors are also under consideration to see if stress increases digestion issues.

His research group monitored feedlot cattle experiencing temperatures of around 0 C, as well as the effect of muddy pens during a thaw.

Mud depth was measured in the pens, especially around the feed bunks and water area.

Meal frequency decreased, but the duration of eating was longer when they came to the feed bunks.

Therefore, environmental conditions affected feeding behaviour but did not seem to increase the risk of ruminal acidosis.

Besides affecting the animals’ overall health, acidosis is associated with other disorders. One study in a slaughter plant found 42 per cent of animals with liver abscesses had compromised rumens.

Another abattoir study of 30,000 head showed most had normal rumen scores but 25 per cent had mild or severe rumen scores. About 67 per cent had normal livers but that means more than 30 per cent of the population had abscesses, said Penner.

The most recent Canadian beef quality audit showed liver abscesses are increasing.

In 2011, the cost of condemned livers was less than $10 per head for an overall loss to the industry of nearly $30 million. The 2016 audit calculated that the economic loss from liver discounts was $20.98 per head for a total industry loss of $61.2 million.

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Reporter/Glacier FarmMedia staff



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