Editor's note: The following article appears in the July 2015 issue of Dairy Herd Management


For today’s modern dairy cow, sub acute ruminal acidosis (SARA) is an occupational hazard — even for herds with a ration including dietary buffers. This nutritional issue can lower herd performance by an estimated $1.12/cow/day in terms of reduced milk production, decreased efficiency of milk production, premature culling and increased death loss.

When rumen pH drops below 5.8 for more than three hours at a time, the time spent below this threshold is known as SARA. A pH of less than 6.0 has negative effects on ruminal cellulolytic bacterial activity and fiber digestion.

In this environment, a cow isn’t prepared to make the best use of any ration — no matter how well formulated it may be. Cumulatively, the rumen environment can spend up to 11.8 hours over a three-day period exposed to SARA, which is almost half a day with impaired digestion.

Unfortunately, most dairy cattle don’t exhibit overt signs of SARA, so the problem is left unacknowledged to silently lower production and lead to increased involuntary culling rates. However, there are several signs that cattle exhibit:


1. Decreased dry matter intake

2. Reduced cud-chewing

3. Mild diarrhea or inconsistent fecal texture

4. Foamy feces containing gas bubbles

5. Reduction of milk yield

6. Reduction of milk component yield and component yield inversion

7. Undesirable cleanliness and hygiene scores

8. Increased incidence of gram-negative mastitis

9. Lameness

10. Reduced conception rates


The most at-risk groups for SARA are fresh cows and high-yielding cows. It is particularly important to monitor these groups for signs of SARA, especially during the summer heat, which greatly increases the risk. Be aware that even cattle fed total mixed rations (TMRs) and in-feed dietary buffers like sodium bicarbonate are still at risk.

Feeding high-forage rations will not necessarily avoid SARA. The majority of forage in TMRs is corn silage, which contains about 0.4 lbs. of kernel processed high-moisture shell corn (kp HMSC) per pound of silage — making SARA a real danger even with higher-forage rations.

What’s the solution? Good feed management practices can positively influence feed bunk behavior, improve feed access and help reduce the time a herd is exposed to SARA.

For example, a TMR that is too dry may allow cows to preferentially sort for grain components and skip forage particles. In addition, feeding unstable or moldy feeds can threaten rumen function and performance.

Optimizing rumen function by adding probiotic feed additives can improve rumen function and increase fiber digestion. In fact, research has shown that cows fed an active dry yeast (ADY) specifically selected to maximize rumen function spend significantly more time above the SARA threshold and even produce 2.1 lbs. more per day of 3.5% fat corrected milk (FCM) per cow per day.

Recognizing the signs of SARA can help the modern dairy cow stay ahead of SARA and maximize production across the herd.


Research citations are available upon request.


Anthony Hall, MSc MSB, PAS, is a member of the ruminant technical services team at Lallemand Animal Nutrition. Phone (315) 727-4820; email ahall@lallemand.com or go to www.lallemandanimalnutrition.com.