CSI-Dairy: A cow-side investigation into feed efficiency & rumen health

Numerous ‘culprits’ exist on dairy farms, robbing herd performance and injuring the dairy’s bottom line. Identifying and arresting the offender isn’t always easy, and often requires a full investigation, gathering and analyzing evidence on the farm and in the lab. One mystery that stumped a dairy producer was evidence of Sub-Acute Ruminal Acidosis (SARA) in an otherwise healthy herd.

By Jerry Weigel

“It’s the strangest thing,” said Don, a dairy producer in southern Wisconsin. “My team has observed symptoms of SARA in the herd, but I can’t figure out what we’re doing wrong.”

I was stumped as well. SARA has been observed in beef feedlot situations by many nutritionists, but in lactating dairy cattle it is a bit controversial.

The investigation

I asked Don all the normal questions relative to the “whys” of low levels of acidosis.

First, I asked about his production, dry matter intake (DMI) and feed efficiency (FE), and learned he was not pleased with the herd’s FE. When we discussed how his team attempted to maximize DMI, I was quick to question the word “maximize.” I told Don I prefer to use the phrase “optimize DMI,” and I believe it is a term nutritionists and producers should use more often.

After learning Don was not pleased with his herd’s FE, I began to wonder if that was a source of his SARA troubles. In my opinion, there could be an interrelationship between SARA and FE. In a time of marginal economics, FE becomes very important as we try to reduce feed costs while increasing the profitability of milk production. As our conversation led back to the relationship between SARA and FE, we discussed a few key points:

Unless the cow is losing body weight, higher feed efficiency means more feed is being converted to milk.

FE and DMI will enable us to determine how well the cows are utilizing the ration.

FE can be improved by reducing other demands for energy or protein.

If the ration is not properly balanced and managed, the ration will contribute to ruminal acidosis (like SARA) and significant reductions in FE, which is especially important.

Improving FE can reduce nitrogen and phosphorus excreted in the manure, a key issue in a manure management program.

I could tell we might be working toward the solution. Then there was another clue – Don mentioned his milk urea nitrogen (MUN) was lower than normal. I explained this could fall right in with the FE, as low MUN can be attributed to questionable carbohydrates, such as poor quality fiber in corn silage and reduced protein conversion efficiency. Another theory is that a too-fragile fiber source that maximizes feed intake could force an increase in water intake, thus having a dilution effect on MUN.

I reminded Don “more” is not always better. We often see high feed intakes on rations with elevated fragile fiber sources. However, rapid passage of the total mixed ration (TMR) can hinder ruminal health. This can reduce a dairy’s FE and, subsequently, its profitability. The rumen must have effective fiber for optimum rumination and microbial digestion.

The follow-up

I felt good that we had found the SARA culprit, and we reformulated the TMR to optimum formulation for sustaining ruminal health. I also put together a list of good management tips around maintaining FE and keeping SARA at bay. Some of these target tips are:

Monitor actual feed intake, pay more attention to feed refusals and improve the record keeping of feed refusals. Put together a budget targeted at a certain percent (i.e., 4.0%), and then base it on a theoretical feed intake of 50 lbs. of dry matter. The targeted feed intake should be 48 lbs. of dry matter.

Correct for milk components, as more nutrients are needed for milk fat and protein than for fluid milk.

Pay more attention to feed bunk management, feed trucks and wagons for feed spillage.

Watch TMR moisture levels and adjust for them on a more routine basis.

Mystery solved

When I chatted with Don a few months later, he was in good spirits. Not only had his SARA situation gone away, but FE had gone from 1.3 to 1.6, with a nice improvement in income over feed cost (IOFC). I reminded him it is important to pay attention to fiber quality and rely more on fiber effectiveness than simply adding more corn to the TMR. However, I also reminded him SARA is somewhat of a management disease, and he must constantly monitor the herd for its symptoms.


Jerry Weigel is the manager of nutrition and technical service for BASF Plant Science. Contact him via e-mail:
gerald.weigel@basf.com; phone: 919-659-3956; or visit www.nutridense.com. Sign up to receive a NutriDense Silage technical dairy e-newsletter, Have You Herd, at www.nutridense.com/newsletter-signup.

Each month, Eastern DairyBusiness will check the case files of lead dairy ‘investigators’ to uncover another ‘CSI-Dairy’ mystery. Episodes will be archived at www.dairybusiness.com.