BANFF, Alta. — Typical feedlot diets rich in highly fermentable grain may help cattle gain weight fast but can also play havoc with their digestive systems.
Ruminal acidosis is often cited as the most common digestive disorder affecting feedlot cattle, although its true prevalence is not fully understood, researcher Greg Penner of the University of Saskatchewan told a recent beef conference in Banff.
The condition occurs when grain is fermented in the rumen and changes the pH value. It produces too much acid, which erodes the gut lining and decreases nutrient absorption. It may also lead to secondary effects such as going off feed, diarrhea, liver abscesses, depression and laminitis.
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“If it drops below pH five, we start to see more detrimental effects and at this point we would classify it as acute luminal acidosis,” Penner said.
“We think these effects are having larger systemic implications for the whole animal.”
Penner and other researchers are looking for ways to mitigate some of the excess acid effects.
“If we are feeding very highly fermentable diets, rumen acidosis is something we need to manage.”
Medicated feed and ionophores such as monensin and lasolacid are widely used in Western Canada to counter the problem.
Adding fibre or increasing fat content so that energy is not reduced is another approach to reducing starch.
Adding more forage to the diet can add more fibre, but Penner said it is not clear whether small increases in the forage inclusion rate have a large enough effect to improve rumen pH.
One study offered more alfalfa hay, which did reduce acid. However, the feedlot industry is not interested because more forage is costly and slows weight gain.
“That is certainly met with disapproval from the industry,” he said.
Experiments have looked at replacing some barley grain or silage with dried distillers grain. The approach reduced dry matter intake, but researchers saw little effect on acidosis levels.
“DDGs have a fairly high fermentability and so they don’t have a lot of effect on rumen acidosis.”
Another approach is to add high fat byproduct pellets such as wheat screenings and off grade canola.
These helped improve the pH balance and did not reduce performance because the cattle still re-ceived adequate energy.
Another approach is to add high fat byproduct pellets such as wheat screenings and off grade canola to help improve the pH balance.
“This looks like it could be one strategy where we could improve the response,” Penner said.
