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Dr. Gary Oetzel, DVM, MS |
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| Click here to download the Journal of Animal Science abstract in PDF form. |
Subacute Ruminal Acidosis (SARA) is likely the most
economically important disorder of dairy cattle in the
United States. SARA occurs when the pH is too low in
the rumen of a dairy cow. The symptoms are rarely noticed
for an individual cow. When a cow’s ruminal pH
is low she responds by eating a little less feed. Her
milk production is reduced slightly, but not to a degree
that would be noticeable.
On a herd level, where the SARA problems start, health
effects have had time to play out resulting in low milk
yield. This can lead to high cull rates and high death
loss. These severe complications of acidosis can take
months to play out after the initial episode.
Dr. Gary Oetzel, DVM, MS, is an associate professor
at the University of Wisconsin-Madison, School of Veterinary
Medicine. He has been researching ruminal acidosis in
dairy cattle for over ten years. According to Oetzel,
the economic impact of SARA is significant.
“It’s a very costly situation for dairymen,”
Oetzel says. “We think it’s probably the
most costly disease condition in the dairy industry
today.” Oetzel says it’s not a matter of
eliminating SARA, but controlling it.
“The way to get milk out of dairy cows is to
get them as absolutely as close to SARA as possible.
Because we want to maximize milk yield, we want to maximize
feeding grains. But we just can’t go over that
line. We are trying to control and manage ruminal pH
and subacute acidosis.”
Dr. Oetzel conducted replicated trials in 2002 and 2004 at the U.S. Dairy Forage
Research Center near Prairie Du Sac, Wisconsin, using
BUFFER-LYX®. Half of the cows in the study had
their TMR supplemented with free choice access to BUFFER-LYX® and the
other half did not. Each cow was on the study for 12
days. Intakes were measured and rumen pH was monitored
throughout the study. In the course of the study researchers
created a SARA challenge.
“We were able to evaluate how the cows responded,
whether they had access to the blocks or not,”
Oetzel says. “We were also monitoring the intakes
of the blocks before and during this acidosis challenge.
“What we found was the intakes were very consistent
with the blocks...between 0.4 and 1.0 pound
per day. They also ate more of their TMR diet. The blocks
seemed to stimulate appetite.
“The cows that had access to the buffer blocks
had a tendency to not lower their ruminal pH as much.
We also saw that those cows recovered faster; they got
back to their normal pH more quickly than the cows that
didn’t have access to the buffer. We also saw
tendencies for those cows not to lose as much dry matter
intake.”
Dr. Oetzel sees the use of free choice buffer blocks
such as BUFFER-LYX® as a “safety net”
for producers.
“Even in herds where producers are doing a good
job nutritionally, there are cows that need that extra
buffering. So we’re going to position this as
an extra safeguard in herds that are still doing everything
else right. The higher the level of production in a
herd, the higher the intake and the higher the risk
for SARA. And as we continue to breed cows to eat more
and milk more, this problem is not going away, it’s
going to get worse. The higher the level of production,
the more likely we are to benefit from something like
this.”
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Cows
that are fed a diet that will lead to SARA will initially
respond much the same as they would in the early stages
of ruminal fermentation. Once the major portion of the
diet is consumed however, cows that were offered BUFFER-LYX®
appeared to handle the increased acid load much better
because BUFFER-LYX® minimized the time cows spend
below a pH of 5.5. In fact, when compared to cows that
did not receive BUFFER-LYX®, they moved to a higher
pH more quickly. The pH of cows that were fed a diet conducive
to SARA and not offered BUFFER-LYX® stayed below
5.5 for a considerably longer time. When diets or feeding
conditions that can lead to acidosis occur, supplementing
with BUFFER-LYX® appears to help cows recover from
SARA and keep fermentation within a more desirable range.
