How to make your dry cows acidic – and make them healthy

The dry cow period should be a wellness break for the cow. Feed composition is vital - especially to prevent disease.

Although the discussion on minerals during the dry cow period was once whether to choose a cheap or an expensive solution, the issue is more complex today. Dry cow feeding has become the new black, and there are as many opinions on what the best solution is for dry cows, as there are consultants. OK, that may be a bit of an exaggeration, but within the field of minerals we do meet a wide range of different opinions and demands as to what is the best solution for dry cows.

Written by: Rikke Kirkebæk,  Nutritionist at Vilomix

The dry cow period is to prepare the cow for the upcoming lactation

It’s not without reason that dry cow feeding has become a hotly discussed issue, as a successful dry cow period lays the foundations for successful lactation. It's generally well known that most diseases in dairy cows occur in connection with calving, or during the start of the post-calving period.

Godden et al., 2003 showed in a large-scale American survey covering 624,614 cows leaving the herds from 5,749 herds, that 25% of those that left the herd did so in the first two months after calving. Financially, this is not the best time to leave the herd!

The dry cow period should be a wellness break for the cow

Because the dry cow period is so important in order to give cows the best possible start to early lactation, it's very important that dry cows are given the attention in the herd they need. The dry cow period should be a low-stress period for the cow, making it important that the dry cow enclosure is not overcrowded, and nor should there be too many group changes throughout the dry cow period.

The emphasis ought to be on providing comfort and hygiene in the dry cow enclosure. Dry cow feeding is important with regard to the correct composition and mixing the ration, to ensure that the cows eat a consistent ration throughout the period. That's why the ration should be broken down, and in many instances, the addition of extra water is necessary, to ensure homogeneity.

Avoid heat in the ration by daily mixing if possible, and adding acid can also be recommended. Strict feed hygiene is a must to be able to keep the cows functioning optimally.

Milk fever - a multifactorial disorder

Milk fever is a problem that the mineral industry encounters more and more often. This might have to be seen in the context of that the dairy cow production having risen considerably in recent years, which puts more pressure on the cows in connection with calving and during the startup period.

What's more, it can be relevant to consider whether the number of milk fever occurrences has actually exploded, or whether increased awareness has simply raised its profile. Whatever the reason, it is a highly relevant problem to tackle, as milk fever can be regarded as being a multifactorial disorder.

When we describe it, we mean that when the cow is ‘cured’ of milk fever – usually through the addition of calcium – then her problems are not necessarily over. Milk fever also often results in other related disorders, such as a higher risk of uterus infection, ketosis, reproductive problems, lower milk production, etc. See figure 1.


Milk fever is a multifactorial disorder that often results in a range of related disorders, which, in the final analysis, can lead to loss of longevity in cows, listlessness and have financial ramifications.

Should we make our dry cows acidic?

How can we solve the problem of milk fever? There are also many answers to this problem, and what works for one farmer, will not necessarily work for the next.

Dry cows in most herds used to be given a ration consisting of the cows’ TMR supplemented by extra straw. This is a practice still in use in a lot of places, and successfully in some herds, but most highly productive cows need their own ration, which takes into account the needs of a dry cow with regard to energy concentration, protein, DCAD (dietary cation-anion difference), vitamin and mineral levels (including extra focus on calcium etc.).

In those herds where it is practically possible, it is very often an advantage to divide the dry cows into a far-off group and a close-up group, as those farthest from calving have a lower energy requirement than those close to calving.

In the battle against milk fever, keeping the DCAD value low is important, especially in the last three weeks up to calving. This can be achieved by focusing on the ingredient composition of the ration, where there can be considerable variation in the DCAD value of different ingredients, or acidogenic (or anionic) salt can be added. And which acidogenic salts should be used is another topic on which there are many opinions.

Magnesium sulphate has a low DCAD value of -16.625 meq per kg dry matter. This is currently one of the most frequently used acidogenic salts, due to the low DCAD value and low price. Magnesium sulphate works best in dry cow rations when only moderate addition of acidogenic salts is needed, as a high level of addition can mean an unsuitably high level of sulphur, which can be harmful to the cow’s rumen environment. But we rarely encounter negative reports on the use of magnesium sulphate in practice.

Another frequently used acidic salt is magnesium chloride, which contributes a less negative DCAD value than the sulphate, of around -9.831 meq per kg dry matter, and is more expensive than the sulphate. Magnesium chloride has the advantage of not contributing sulphate to the dry cow ration, and is water-soluble, in common with the sulphate. When a high level of acidogenic salts is needed to reduce the DCAD value to a low level, combining the addition of magnesium sulphate and magnesium chloride can be beneficial.

Ammonium chloride can also be recommended for acidifying dry cows, but because it needs HACCP approval, adding it through a dry cow premix is recommended. The advantage of using ammonium chloride is that it does not add magnesium, which the cows will get plenty of through the use of magnesium sulphate and chloride, if the dry cow ration already adds magnesium from, for example, phosphate or oxide. When acidifying a dry cow ration, it’s important to remember that the acidifying salt tastes bitter for the cows, and it's important that they are not put off the feed, which can also give major problems when it comes to calving for the cow and the calf.

How far down the DCAD value has to go in the close-up ration to prevent milk fever can vary enormously between herds. A good indicator of a suitable level is urine pH value. If it lies between 5.5-6.5, experience shows that milk fever is rare. In some herds, getting the DCAD value down to around 0 meq per kg dry matter is sufficient, while others need to get down to -100 meq or lower to avoid milk fever in the herd.

Is dry cow feeding a jungle?

If we return to the earlier question of whether dry cow feeding has become a jungle, we could be inclined to answer: yes, it has.

But having said that, what it may really be is that there is no clear answer in practice to how milk fever can be avoided. In theory, cows fed on a barren ration with a low DCAD value should not contract milk fever, but, as is so often the case, theory and practice do not always go hand in hand.

What's more, we can find that, in practice, producing the ideal dry cow ration is impossible in every herd, because the conditions will simply not allow it. It could be the conditions inside the sheds, the feed, the amount of available labour and so on, all of which can affect the herd. As is so often the case when working with cows, good management and proper care are key to preventing milk fever and other problems related to calving.