Eamon O’Connell: What dry cow minerals to buy and how best to feed them this winter

I dutifully drove the jeep into the shed along the feed fence where my sick patient was waiting for me. She was a fourth lactation cow who had calved last night. In this autumn herd, 25 cows had already calved and this girl was the first to cause trouble.

The cow in question was lying in her cubicle bed and behaving as if she were fast asleep. The farmer had tried unsuccessfully to get her to get up, but she was much happier with her head cocked to the side in the sleeping position. I had a vague idea of ​​what the problem was, but I proceeded with my clinical investigation anyway.

She did not have a high temperature and had passed all cleanings shortly after calving. I’ve been looking for replacement parts and cracks and luckily couldn’t find any. The term “tears” is self-explanatory and “spares” refers to a second calf still inside the cow.

If you are ever unlucky enough to let a second calf in a cow, I guarantee you will not let it happen again. The cow had neither mastitis nor signs of pneumonia. My suspicion was correct – she had milk fever.

The farmer told me he had already put two vials of calcium under her skin because he suspected the same, but she hadn’t responded. In most cases, a bottle in the vein works wonders and in the case of this lady we were not disappointed.

As soon as the last drop had run in, she recovered Lazarus-like and stood up. It’s a great feeling to have such an immediate response, and milk fever is one of the few conditions where recovery can be so quick.

In the past, the vet would have washed up at this point and taken to the streets.

Now, in the age of herd health and a proactive approach, any sick animal should be prompted for evaluation and a plan to prevent further cases.

A single cow with milk fever is just the tip of the iceberg. For every cow with milk fever, there are up to 10 more in the subclinical form. Just because you can’t see it doesn’t mean it’s not a big problem. Cows with clinical or subclinical milk fever are automatically in the so-called “milk fever cascade”.

Once a cow has some form of milk fever, there is a cascade of related problems that affect her throughout lactation. Their gut motility is reduced and so is their feed intake by default. Less food means less energy, which can lead to conditions like ketosis, fatty liver, and poor performance in general.

Less feed also means less rumen filling, which leads to displaced abomasums. An overall negative effect on the cow’s immune system makes her susceptible to developing mastitis.

As an aside, it always pays to keep a close eye on cows being treated for milk fever. They often develop a very nasty mastitis over the next few days. Sometimes a cow with milk fever will have severe mastitis at the same time, so it’s always worth checking all four quarters, even if they’re difficult to get to.

The truck I had made room for arrived just as I started my conversation with the farmer about milk fever prevention. “Give me five minutes to unload this yoke and then we’ll go through the whole pile,” he told me as he climbed the steps of his recently purchased tractor.

In the past few weeks, some new tractors have been arriving on the farms, and I’ve heard a wise old farmer refer to them as “Inland Revenue tractors.” Farmers who have a lot of money this year would rather spend it on a new tractor than spend it on earnings.

As it turned out, the pallet he unloaded contained the product that is the cornerstone of milk fever prevention — dry cow minerals.

Everyone has the general idea at this point. They shake minerals onto the silage before calving to prevent milk fever and ensure a healthy immune system after calving. Easy. Well, maybe not that easy.

First, there are so many different dry cow minerals on the market, each containing different concentrations of minerals. Take magnesium as the key ingredient.

Dry cows require 42 g/head and day of dietary magnesium to prevent milk fever. The magnesium content can vary from 20 to 28 percent depending on the brand of dry cow mineral.

When the silage being fed is low in magnesium, every extra gram of dry cow mineral counts. The next thing to consider is how the mineral will be fed. Mixing it in the feed trough seems like the best option, but it turns out shaking it over the silage is better.

This is due to the fact that as the calf grows larger inside the cow, the cow’s ability to eat decreases.

When the mineral is mixed into the silage, the cow that needs it the most will get less as she eats less the closer she gets to calving. If you get caught for feeding, shaking the mineral on the silage twice a day will help ensure all cows are getting what they need.

You’re probably wondering why I’m even talking about dry cow minerals at this time of year. Well, Christmas is less than three weeks away, which means the start of calving is less than eight weeks away on many farms. Ideally you should be feeding minerals six weeks before calving, so it’s time to order.

But before you do that, have your silage analyzed. There are many labs that do a complete mineral profile of your silage. This way you know what you have and what you need.

Here is how you should buy your dry cow minerals rather than buying a specific brand because they are cheap or come with a free pair of rubber boots.

Also do the calculations.

Check the recommended feeding rate – many brands recommend feeding 100g/head per day. For a herd of 100 cows, this means that a 20 kg bag will last only two days. Buy enough and make sure the vet won’t get in the way of delivery.

​Eamon O’Connell is a Veterinarian at Summerhill Vet Clinic, Nenagh, Co. Tipperary.