A blood test can reveal hidden issues

So, it turns out I have high cholesterol. I “got my bloods done” at my GP surgery last month. I’ve been meaning to get checked out for a long time and I’d been putting it off. It was only when I was chatting to a farmer while calving his cow that I was pushed to act.

He had just been for a check-up himself and when I told him that I hadn’t been to the doctor in over five years, he got quite exercised. “You’ve young kids, a growing business and a good wife. You should be getting an NCT every year,” he said, pretty much scolding me.

“You wouldn’t wait till the oil light was on and the jeep was blowing black smoke before you went to the garage,” he said. He was right, and when the results came back, in truth, I wasn’t surprised. Recently, my diet has been terrible, my exercise regime has been erratic, as well as my genetics predisposing me to elevated cholesterol levels. It’s the kick in the backside I badly needed and, already, it is very noticeable that the treats in the clinic tend to last longer now that I’m not nibbling away at them all day.

When it comes to animal health, blood testing is at the core of any diagnostics we perform on farm. There can be many diseases or issues in individuals or groups of animals that are not visible to the naked eye but are eating away at animal health and at farm profits.

Let’s start with calves. Sheds are full of them at present and we are seeing lots of sick calves with both pneumonia and scour. When we are investigating any calf disease issue, we will take some bloods from very young calves to check the total protein level. This tells us if they have received enough good-quality colostrum in a timely fashion. Recently, a new calf-side test has come on stream that can be used on calves up to 42 days. This is a super tool when dealing with disease outbreaks, as it allows us to look back almost six weeks previously and see whether colostrum management was up to scratch or not.

If a group of tested calves are above the acceptable threshold level, then a clap on the back is all that’s required, and keep up the good work going forward. However, if calves fall below the acceptable level on the test, it’s time for a full and frank review of colostrum management protocols on farm. Additionally, because these calves haven’t received enough protective antibodies after birth, they are much more susceptible to infectious diseases.

Also, they are unlikely to have received other important components such as hormones and growth factors — both of which are vital for development and future productivity. A serious overview of management practices needs to be undertaken with your vet and some tough decisions may be needed on the future of some of these calves in the herd.

Moving on to the next group of animals on the farm — the maiden heifers. Even though you might not want to think about it, these heifers will be getting served in five weeks’ time or thereabouts. So, it’s time to get organised for the breeding season, even if the weather isn’t playing ball.

The weather, along with struggling milk prices, has led to an increase in the number of times lately that I have been asked: “Do I really need to vaccinate for X disease?” Be it IBR, Lepto or BVD, the temptation is to roll the dice in an attempt to save money. My gut instinct is to tell you to vaccinate your heifers for all of the above to ensure they go in calf, stay in calf and, after milking well in their first lactation, go back in calf again in a timely fashion.

However, if you need convincing, blood-testing eight to 10 heifers will give you a nice insight into the diseases that they have been exposed to. Antibody levels to IBR and Lepto in particular give a good guide to the circulating levels of disease in an unvaccinated herd and the urgency to vaccinate if needed.

As for BVD, we are on the home stretch when it comes to eradicating the disease so continuing to vaccinate for another while could mean the difference between getting rid of it entirely or letting it reignite from the tiny embers that are still smouldering in some parts of the country.

Where blood testing really comes into its own in heifers is for minerals. Minerals such as copper and selenium are often overlooked as causes of poor fertility in heifers. We are guilty of presuming that if heifers meet their target weight, they are ready for bulling. Then, we scratch our heads when conception rates, particularly to fixed-time AI and sexed semen, are below par.

A blood test on some of the heifers now could highlight a mineral deficiency that could be easily corrected before breeding starts. This might be the difference between a super breeding season and one whose end result is heifers still waiting to calve at the end of March 2025.

In cows, a mineral profile is of equal importance pre-breeding. When selecting cows to blood test, it’s worth focusing on first and second calvers as these are under the most pressure in early lactation. Don’t presume “there’s enough minerals in the nuts” or “sure, I fed them minerals all winter, they hardly want more now”. A blood test will reveal all, and your vet will advise you on supplementation options. Similar to the heifers, Lepto and IBR status can be ascertained through the same bloods that are used to check mineral status. So, before you get some cows blooded, have a good chat with your vet as to what exactly you want to test for.

Blood testing is useful in very recently calved cows to check for “transition” issues such as ketosis or subclinical milk fever. Bloods from cows on the point of calving can be checked for magnesium status and from very recently calved cows for calcium. This will clearly show if there’s any issue with invisible, subclinical milk fever. Similarly, recently calved cows can be tested for levels of BHB, a direct indicator of ketosis.

There are some cow-side tests that we use on sick cows to help our diagnosis. Any sick cow that has calved recently is at risk of ketosis. A ketone meter is a pocket-sized device that gives a reading of ketone level in a few seconds from just a small drop of blood. This allows us to adjust our treatment protocol in these sick cows to greatly improve their chances and speed of recovery. Last week, I briefly mentioned diagnosing a cow with peritonitis. I took a sample of blood from the affected cow and put it into a special tube. The time it takes for the blood to clot is an indicator of the level of inflammation in the cow. If the blood clots in less than five minutes, there is a high level of acute inflammation in the affected cow.

During the week, I was called to see a sick cow that was passing reddish-coloured urine. The farmer was worried that the cow had “redwater”, a tick-borne disease whose main clinical sign is dark red, almost port-like urine. This cow’s urine resembled more of a rosé prosecco than port, so I took a blood sample and made a blood smear to examine it under a microscope. Our nurse confirmed that the sample was free from textbook signs of redwater, and the cow recovered with just close monitoring.

Blood tests can confirm lots of issues that we might suspect on farm. Like my cholesterol, you need to find out first and then go fix the problem.

‘ When selecting calves to test, focus on the first and second calvers as these are under the most pressure in early lactation’