Practice Management: A closer look at metabolic profiling
Metabolic profiling and its results have disappointed me several times during my career. Yet I recently had success using an approach promoted by University of Wisconsin (UW) associate professor Dr. Gary Oetzel, who believes two subclinical syndromes account for a large percentage of dairy farms problems.
These two syndromes are subacute ruminal acidosis (SARA) and subclinical ketosis (SCK). Cows suffering from these conditions have depressed immune function and are at risk for other disease syndromes. Cull rates on herds with these syndromes tend to be high.
Oetzel's strategy was presented by UW veterinary school staff during the 2004 American Association of Bovine Practitioners' annual convention.SCK diagnosis
Subclinical ketosis can be evaluated by measuring beta hydroxybutyrate levels in cows during their first 30 days post calving. The Wisconsin group suggests that if 10 percent or more of these animals are elevated, subclinical ketosis is probably a problem in the herd.
If we sample 12 cows from this stage of lactation and find three or more elevated values, we can predict with a 75-percent confidence interval that SCK is a problem. While researchers generally like a much higher confidence interval, a working dairy herd is not a laboratory, and the potential cost of ignoring a problem when we are 75 percent certain it exists makes no sense.
When subclinical ketosis exists in a group of fresh cows, we need to know the cause. It often is difficult to locate any deficiency of fresh cow management. Rations appear sound, bunk space is adequate, comfort is acceptable, yet too many cows are not doing well. In these cases, it helps to address pre-fresh animals.
Cows that experience significant energy deficiency prior to calving tend to have an increased level of post-calving problems. A test to determine an animal's energy status is non-esterified fatty acids (NEFAs). These values are elevated when cows burn fat to meet energy needs. While they're expected to rise post-calving, they should be normal prior to delivery.
NEFAs should be evaluated in cows that deliver two days to 14 days after sampling. This presents a problem, since we never know precisely when a cow is going to deliver. Also, in small herds, we often do not have enough animals in this group for meaningful samples.
To get around this, draw ethylendiaminetetraacetic acid (EDTA) samples for all cows within 20 days of freshening, separate the plasma and freeze it. Do this until you have at least 12 from cows that deliver their calves within two days to 14 days of the sampling. The frozen plasma can be tested. If four or more tested animals show elevated NEFA's, a problem likely exists in the pre-fresh management.
Many people believe SARA can be assessed through milk-fat percent, milk fat/milk protein ratios, degree of cud chewing and manure consistency. Oetzel suggests these parameters might appear normal although rumen pH drops to low levels between six hours and 10 hours after a cow ingests a large meal. He suggests the best way to access SARA is to tap rumens on cows with high dry-matter intake between six hours and 10 hours following first exposure to their daily TMR.
Most cows do not enjoy having a needle inserted into their rumen, but if they are properly restrained and distracted with the judicious use of a nose lead, the procedure can be completed with minimal distress to the cow or the doctor. Use a 16-gauge, 4-inch disposable needle to insert into the rumen just behind the last rib at the level of the stifle, and withdrawal roughly 1 ml of fluid. This can be tested with an electronic pH meter. Cows showing a pH below 5.5 are acidotic. If more than four of 12 tested are below that level, a herd problem likely exists, again using a confidence level of 75 percent.
In addition to the tests described, others can be used to add information. Total proteins from serum reflect long-term protein intake, while serum urea nitrogen is a barometer of balance of nitrogen to nonstructural carbohydrates. Calcium levels from cows taken the day after calving will demonstrate, if subclinical, hypocalcemia is part of the problem. I often have taught lay staff to collect these samples and left a centrifuge on the farm so they can separate and freeze the serum until we have enough samples for the lab.
Functionality of metabolic profiling