Milk fever in dairy cattle is a well-known disease, which primarily occurs in older cows in connection with calving. The disease is characterised by the cow being cold, rolling and maybe paralysed. The disease is often combined with the cows yielding less milk, and the cows have an increased risk of developing mastitis, metritis and ketose – all diseases which influence the animals’ welfare and the farm economy significantly. The occurrence of milk fever at organic farms is higher than at the conventional farms. Previous studies have even found considerable differences in the occurrence of milk fever at herd level within the group of organic farmers without being able to explain why.

A new interview study from Aarhus University now shows that the farmers assess the problem in very different ways and that the occurrence of milk fever is very dependent on summer pasturing. The study also shows that many organic farmers are critical of the legislation, which prevents them from treating the milk fever with calcium directly into the cow’s vein, and that the organic farmers are working with different strategies when it comes to prevention.

In this study, 56 organic farmers with herds of more than 100 cows have been interviewed over the telephone about their understanding of milk fever, their practical procedures regarding prevention and how they deal with milk fever. The answers have been analysed and compared to data from the herds from the Danish Cattle Database.

Not a problem, but then again

From the 56 farmers, 38 answered that they did not think that they had a problem with milk fever. One justified it by saying that even though the vet thought she had a problem, she has chosen to accept that milk fever was inevitable, especially in old (fourth lactation or older) and slightly fat cows. Others accepted the problem but tried at the same time to reduce it, for instance to a condition which only happens periodically. Furthermore, the problem was related to certain seasons, to the ages of the cows and to human handling. Twenty-six farmers answered that they found milk fever to be a very problematic condition also because of secondary complications, such as retained placenta, mastitis, ketose, reduced yield and abomasal displacement. One farmer explained that when treating for milk fever, there were no complications, not even with secondary complications. However, if not treated in time, further complications occurred.

The law as part of the problem

Twenty-five of the farmers expressed that they had a hard time understanding why they were not allowed treating the cows with calcium in the blood themselves as the rules in the organic regulation state. Several pointed to the fact that they do understand that only the vets are allowed to treat with antibiotics, but they do not understand why it is also the vet who administer the calcium. From a scientific point of view, this group thought that arguments were lacking as to why they were not allowed to treat with calcium. According to some of the farmers, the law created a dilemma about economy. Paying a vet, because the farmer was not allowed to treat the cows himself, could result in postponing the treatment. Furthermore, some omitted the pain treatment when giving calcium in the blood because analgesic drugs count in the treatment accounts even though it is not antibiotics. The reason for this was that an organic cow could only be treated three times during 12 months to keep its organic status. Several of the farmers pointed to the fact that the method they in fact were allowed to use, which was to give the cow the calcium orally, was a method they did not find scientifically good enough, because the organic products, which are considered having a sufficient effect, do not exist.

The farmers who did not see the regulations as a problem pointed at a basic perception of being ecologist: You have to adapt to the rules. Others argued that milk fever should not even occur, and that one should focus on prevention and not on the rules.

Comprehension and prevention

The majority of farmers recognised a cow at risk of milk fever via classical symptoms: cold on the muzzle, tail head and ears. Furthermore, they mentioned the cow’s appetite and observations of the cow’s behaviour. In the case of bad welfare and appetite, half of the farmers replied that they had a calcium product for oral use with which they treated the cow – either by routine or to specific cows at risk.

To the question about prevention of milk fever via feeding, almost all farmers focused primarily on good feeding of dry cows, for instance by using a separate dry-cow blend and dry-cow minerals. The farmers’ answers varied much in the choice of methods of drying off where some used an abrupt withdrawal (the cow is fed straw and water for a period to stop the milk production), while others supplied their cows with hay, silage, wrap or a dry-cow blend. The farmers also differed much when speaking of feeding of dry cows during summer and winter. For instance, the feeding was almost the same during winter and summer for some, while others replied that they supplemented the grass with dry-cow minerals and allocated feed according to needs. No one used analysis from a laboratory prior to the decision on harvesting, but a single farmer was so unsatisfied with the quality of the silage that he decided to use grass analysis in the future.

Coupling to data of milk fever

All interviewed farmers gave the researchers their permission to collect the farm’s data from the cattle database from 2016 on registered calving, and all occurrences of milk fever were listed. The number of percentages of milk fever in cows of third parity or more in 2016 in the 56 herds varied from 0% to 14.9%. The 10 herds with the fewest registered occurrences were herds where all owners mentioned good dry-cow feeding as the most important preventing initiative, whereas the group with the most registered occurrences of milk fever to a higher degree mentioned minerals and calcium products as means of prevention. In the group with the fewest occurrences of milk fever, seven out of 10 producers fed their dry cows in the same way when grazing during summer and winter. In the group with the most occurrences of milk fever, only two out of 10 producers supplied the grazing with another feed.

A surprise

It was a surprise to the researchers that this many organic farmers expressed in the interviews that they did not have problems with milk fever in their herd. If the 38 farmers who answered that they did not have problems corresponded to the 38 in the database with the fewest occurrences of milk fever, it can mean that they accepted that up to 6.1% of their third parity cows or older suffer from milk fever.

Besides, so far, we can conclude that correct summer feeding of dry cows is very essential in relation to prevention of milk fever. Previous studies have shown that grazing cows are at higher risk of developing milk fever, and this study confirms this statement. This study also shows that there is a difference in the occurrence of milk fever at summer feeding (primarily grass) compared to cows fed almost the in same way all year round. On the other hand, this study cannot tell anything about the significance of the difference of the types of winter feeding. This may be because the farmers have different descriptions of how dry-cow feeding is allocated. The next phase of this study will also include going into this matter in depth.

Facts about the project

The interview study is part of the project “Prevention of milk fever in organic dairy herds”, which is supported by Mælkeafgiftsfonden. The project leader is Heidi Voss, vet and scientific assistant at Department of Animal Science, Aarhus University. The project is organised in three phases where the first phase is an interview round with a succeeding final report. Phase 2 is the organisation of a workshop in cooperation with the consultants where the results from phase 1 will be presented and discussed in order to receive further input to phase three. Phase 3 consists of visiting herds of various occurrences of milk fever in order to clarify detail procedures causing the differences and development of the final product: the best practice for prevention of milk fever in organic dairy herds. The advice emerging from “best practice” will be available to all organic milk producers.