As I have written before, dairy cow production and health has improved to such an extent that major diseases that impact production are now as likely to be ‘subclinical’ as they are to be clinical. By subclinical, I mean that it is not easy to see that a cow or calf is sick. You might only find out that it is sick by doing some sort of test. The oldest test that we still use today is the California Mastitis Test, an old standby to find quarters with subclinical mastitis. It has all the attributes of a great test: it is cheap, convenient, easy to use and fairly accurate.
Another great test that is commonly used is the BHB test to detect subclinical ketosis. BHB stands for beta-hydroxybutyrate. The BHB test replaced the milk ketone test as a way to find cows with subclinical ketosis. Cows with subclinical ketosis often have reduced production and are more likely to get other fresh cow diseases. The BHB test is widely and often routinely used now to detect ketosis early so cows can be treated more effectively. There are guidelines on which cows to test and when to test so dairy farmers get the most efficient return on their investment in testing.
Another subclinical disease that is very common in older cows and in some fresh heifers is subclinical hypocalcemia — blood calcium is low but not necessarily low enough for cows to go down with clinical hypocalcemia, milk fever. Veterinarians started paying attention to subclinical hypocalcemia (SCH for short) a few years ago. Research had found that cows with SCH at freshening were more likely to go on to have other health problems like DA’s, RP’s, ketosis and metritis. There is evidence that cows with SCH may also be less productive.
It is not very easy or convenient to test for SHC. You need to test blood and you need to test the blood quite soon after you take the sample. The machine that detects blood calcium is not very portable so vets wouldn’t usually get results right away.
A few years ago, researchers at Cornell University started to work with a company to see if they could develop a machine to test blood calcium that could be used in barns similar to the little meters that are so convenient to test cows for ketones/BHB. After quite a wait, it seems as if that calcium meter might be close to becoming a reality.
The company that makes a blood calcium test meter had it on display at a conference that I attended at the end of August. It is intended to be used in barns. The company planned to have it available in North America in the fall of 2018. The calcium meter will work a little differently than the ketone meter. The ketone meter uses little test strips to detect BHB. The calcium meter does not use test strips but it does use test solutions. The test solutions are needed to make sure that the calcium meter is measuring accurately. Replacing test strips is part of the costs for using the BHB meter; replacing the calibration fluids as they get used up will be part of the costs of using the calcium meter. Still it will be difficult to beat the convenience of being able to measure blood calcium right in the barn. It could be used on cows with clinical milk fever, not just cows with SCH.
Getting a quick and easy way to test cows for low blood calcium will be a big help to becoming better able to manage fresh cows and close up dry cows. Like all new technologies, though, there will likely be a learning period. We’ll need to figure out the best time to test cows and the level of blood calcium where we’ll need to be concerned and take action.
Dr. Robert Tremblay is a veterinarian for Boehringer-Ingelheim and lives near Guelph.
