Cows will naturally go through a negative energy balance when they enter into lactation as their body adjusts from the dry period into milk production. We know, though, that problems start cropping up when that negative energy balance persists for longer than what the body can deal with. That’s when metabolic issues like ketosis occur.
Ketone bodies are an alternative energy source, so the cow’s body will begin producing more of them when the animal is in need of energy. But too many ketones can cause disease that can be both clinical and subclinical. Clinical ketosis is identified when cows reduce appetite, have the classic ketone-smelling breath, and may go down. Subclinical ketosis is, of course, harder to detect. It is often characterized by fatty liver, and it’s estimated that about one-quarter of U.S. dairies are affected by it, said Penn State Extension dairy educator Michal Lunak.
“Obese cows are prone to subclinical ketosis much more than cows that aren’t overconditioned,” he noted on an episode of the “Bovine Banter” podcast.
Lunak outlined that research has estimated a case of subclinical ketosis to cost between $120 and $300. But there are also the longer term effects on the animal’s body and overall health that can last for the rest of a cow’s productive life. Another study of a 400-cow dairy approximated that subclinical ketosis cost the farm between $4,100 and $6,000 each year.
Cows with subclinical ketosis range anywhere from three to 19 times more likely to contract a displaced abomasum, he cited, and they are 7.2 times more likely to get metritis. Overall, they are about three times as likely to be removed from the herd as cows without ketosis. “That’s the ultimate cost,” Lunak warned.
Peel back the curtain
So, how do we know if this subclinical concern is a problem in our herd? If you know clinical ketosis is an issue, cow-side blood, milk, or urine tests for ketone bodies can help find subclinical cows. Lunak recommended the blood tests as most accurate.
Since tests can be expensive and time-consuming, Lunak offered another way to gauge if more investigation into ketosis in the herd is warranted. Using milk testing data, calculate animals’ milkfat to protein ratio. Typically, this ratio would fall between 1.2 and 1.4. If 40% or more of the herd has a ratio of over 1.4, you may be dealing with a ketosis problem, he said.
This calculation can be performed and graphed in herd management software systems for a quick view of the herd’s status, Lunak added. While we don’t want to come to a conclusion based on just one indicator, fat to protein ratio is one place to start when determining if ketosis could be an issue. Also look at the scope of the problem to see if it could be a herd concern or is only limited to a smaller group of animals.
Lunak noted that these calculations could be done with different datasets to monitor specific trends. Do it by lactation number to see if older cows may be having more of a problem with ketosis, as they are prone to do. Do it by group to determine if there is a difference in one ration or another. What ketosis issues often boil down to, Lunak said, is nutrition, feed access, cow comfort, and time away from the pen.
