When milk prices are good, dairymen often focus on maximizing production and sometimes lose sight of issues that are costing them money. When milk prices are low, dairymen are much more interested in these money-losing issues. Such is the case with undiagnosed metabolic diseases. We have all seen figures on costs associated with dead cows and treatment of various diseases. But what about the cases that go undiagnosed? Is this a problem and is it economically worthwhile to evaluate and correct? The answer to these questions is a resounding ‘YES.’

Traditionally diseases have been classified as either clinical or subclinical. Clinical diseases show recognized symptoms that are often confirmed with various diagnostic tests such as blood analysis. Subclinicals are the exact same diseases without recognized symptoms, leaving them to only be diagnosed based on results of diagnostic tests. Because we do not test every cow for every disease, subclinical also generally means undiagnosed.

In the case of metabolic diseases, hypocalcemia (milk fever) and ketosis are by far the two most important diseases to consider for early lactation cows. Both of these diseases are referred to as “iceberg diseases.” This is because clinically we only see the tip of the iceberg (about 1 to 10 percent of all dairy cows that calve for each disease). On the other hand, various research studies show, on average, the subclinical rates of these two diseases may average about 40 percent each in modern dairy cows. This large discrepancy makes designation as clinical or subclinical irrelevant for metabolic diseases. The large amount of undiagnosed cases is the crucial point.

But are undiagnosed metabolic diseases really costing dairymen anything? Numerous cost estimates for clinical metabolic fresh cow diseases have been calculated over the years. We know part of the cost for clinical diseases is the actual treatment needed to cure the animals and the losses suffered when cows that do not respond to treatment leave the herd. The part that is often forgotten is the effect on milk production for the entire lactation and losses in reproductive performance and associated added feed and fixed costs. This part of the economic equation is not that different for clinical or subclinical presentations, and makes up the losses associated with undiagnosed cases.

As an example, let’s look at ketosis. Cornell research has estimated the inclusive cost of a clinical case of ketosis at $151. If we use an average clinical observation of ketosis (5 percent), then clinical ketosis costs the dairyman about $7.55 per cow that calves. On the other hand, researchers at the University of Guelph estimated the cow performance cost of subclinical ketosis at $78 per case. Since the overall average occurrence of subclinical ketosis is close to 40 percent, it costs the dairyman an average of $31.20 per cow that calves. Potentially, subclinical (undiagnosed) ketosis costs the U.S. dairy industry more than four times as much as the clinical presentation. Hypocalcemia follows the same pattern. What you don’t see can cost you a lot!

Today we know that ketosis and hypocalcemia also have an association with disruption of other metabolic system functions that add even more hidden costs. Hypocalcemia has been associated with reduced immune system function and increases in the risks of mastitis and metritis. Subclinical ketosis has been associated with a 40 percent decrease in first-service conception rate, a 16-22 day increase in days open, doubling in the rate of endometritis, and decreases in immune function.

The economic impact of these complex associations is difficult to pencil out. In today’s dairy economy, it is likely that the average occurrence of undiagnosed hypocalcemia and ketosis costs the dairyman at least $50 for every cow that calves. The figure is probably two to four times higher in reality. Let’s look at it in a different way. In today’s dairy economy, how would you like to add $40, $50 or even more to the net income of every cow lactation on your dairy? That is the possibility by managing subclinical metabolic diseases.

What to do
The first step toward improvement is to identify what the rate of metabolic diseases is for your dairy. Hypocalcemia is easily detected by measuring blood calcium levels immediately after calving. An occasional screening of a number of samples of blood by your veterinarian can give you an indication of where you stand. If you already have a cation-anion balancing program in place, urine pH can be a helpful indicator.

Ketosis is a little more complicated. Both the incidence and duration of ketosis are important factors. Ketosis is usually most prevalent one to two weeks following calving. As cows eat more and improve their negative energy balance, ketone levels in the blood decrease. This usually occurs between two and four weeks of lactation, but can last longer. Cows with ketosis lasting longer into lactation generally have more reproductive issues.

Blood testing for ketosis historically has been cost-prohibitive. Alternative tests for milk or urine ketones are not sensitive enough or quantitatively accurate enough for much practical use in screening programs. A relatively new method of measuring beta hydroxy butyric acid (BHBA) in blood using a human diabetes/ketone meter and test strips has been found to be both very sensitive and quantitative as a cow-side test. Your veterinarian can quickly test a representative sample of post-calving cows and have results immediately. It becomes a little more complicated and costly to analyze the duration of ketosis in early lactation cows, but it can be done.

Testing a representative sample of cows for hypocalcemia or ketosis could be done for a couple of hundred dollars and would indicate your current herd status. Alternatively, you could believe the vast amount of research and assume a high subclinical incidence of both diseases in your herd. Then, any management practice that improves blood calcium status at calving and overall energy balance and blood glucose status in early lactation cows probably makes excellent economic sense.

Parturition complex
“Parturition complex” encompasses the numerous interactions of hypocalcemia, ketosis, low blood glucose and immune system suppression present at calving. If 10 percent or more of your cows end up in the hospital pen at any time during the first 30 days of their lactation, you likely have parturition complex issues that are costing you a lot of money. This is even likely if you identify many of your hospital pen problems in the category of infections, such as retained placenta/metritis.

Other performance parameters that can indicate parturition complex issues include high number of cows leaving the herd within 60 days of calving, lower transition cow index scores, low first test milk production, inverted fat and protein percentages at first test, reduced or delayed peak milk, excessive body condition score losses in early lactation, pregnancy rates below 20 percent even with a synchronization program, high prevalence of cows with inactive ovaries more than 60 days in milk, and others.

Milk prices may be depressed, but, especially now, you can make money by managing undiagnosed metabolic diseases. Maintaining this management when milk prices increase will earn you even more. PD

References omitted but are available upon request at editor@progressivedairy.com

• William Zimmer

• DVM
• Bio-Vet, Inc. bzimmer@mhtc.net