Milk fever in dairy cattle is a well-known disease, which primarily occurs in older cows in connection with calving. The disease is characterized by the cow being cold, rolling and maybe paralyzed.
The disease is often combined with the cows yielding less milk, and the cows have an increased risk of developing mastitis, metritis and ketosis — all diseases that influence the animals’ welfare and the farm economy significantly.
The occurrence of milk fever at organic farms may be higher than at the conventional farms, according to researchers at Aarhus University in Denmark. 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 now shows that the farmers assess the problem in very different ways and that the occurrence of milk fever is very dependent on access to summer pasture.
The study also shows that many organic farmers are critical of legislation in Denmark that 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, Aarhus said.
In this study, 56 organic farmers with herds of more than 100 cows were 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 analyzed and compared to data from the herds from the Danish Cattle Database.
From the 56 farmers, 38 answered that they did not think that they had a problem with milk fever. One farmer explained that even though a veterinarian 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 that only happens periodically, according to Aarhus. 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, ketosis, reduced yield and displaced abomasum.
Twenty-five of the farmers expressed that they had a hard time understanding why they were not allowed to treat the cows with calcium in the blood themselves as the rules in the organic regulation state, the university said. 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.
Several of the farmers pointed out 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 calcium products that are considered to have a sufficient effect do not exist.
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, Aarhus said. 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 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, according to the university.
Coupling to milk fever data
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, Aarhus said.
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.
So far, the Aarhus researchers concluded 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.