In regular milk recording all milk samples are now also analyzed for the ketone substance beta-hydroxybutyrate (BHB). The aim of this decision by RYK is to provide a quick and inexpensive monitoring of whether the herd has subclinical ketosis among cows in early lactation*.
The results can be seen on the report "Laktationsnøgletal BHB", which can be retrieved from the Cattle Registration Program, or it can be ordered from the local RYK office.
Threshold values from abroad
By interpretation of the results, the focus is not on the amount of BHB in the milk of the cow, but on the share of cows in a well-defined group that exceeds a defined treshold value.
The analysis of the BHB in milk recording samples is new in Denmark, and we do not yet have Danish data to define threshold values. We must look to the other countries that use the same measurements. Here we find a a suggestion for threshold values in the Canadian State of Quebec, which has analyzed the BHB in the milk since October 2011. There are also several years of experience with the method from the Netherlands. According to these foreign data the threshold on elevated BHB in the milk is 0.1 mmol/l, and herds with many cows over that threshold typically have a problem with subclinical ketosis.
Only cows in early lactation are interesting
The simple way for the laboratory is to analyze all the milk recorded cows for BHB, but the primary interest is on results from cows in early lactation, and the focus should be on results from cows, which are milk recorded 5-35 days after calving.
Typically there will be individual cows with elevated BHB in most herds. Of course, it is important to have a greater focus on these cows. But the most important thing is to focus on whether the proportion of cows in early lactation with BHB above the maximum level is high. In such case it is a problem that should receive a great deal of attention in herd management.
A relevant key figure is therefore "share of the cows in early lactation with high BHB," and based on the foreign data our preliminary guidance for interpretation is:
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< 30 % of fresh calvers have BHB > 0,1:
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No indication of general herd problem
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30 -50 % of fresh calvers have BHB > 0,1:
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Closely monitor developments in the herd
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> 50 % of fresh calvers have BHB > 0,1:
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Many cows with critical values.
Interventions to be considered
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Important is to be aware that in order to get valid results there must be about 10 cows in each group, before a calculation of the proportion of cows with elevated BHB values should be made. Otherwise, information from multiple milk recordings may be used in order to get a valid monitoring.
Why is there a BHB in the milk?
A high content of BHB in the milk suggest that cows mobilize so strongly that the liver has not sufficient capacity to transform all of the fat coming from fat tissues. This means that ketone bodies, — a by-product from an incomplete metabolism of fat, builds up in the blood. At the same time, there will be traces of ketone compounds in milk and urine.
Cows with elevated BHB will often be the same, which have high body fat percentage and elevated Fat-Protein Ratio in milk.
Symptoms of subclinical ketosis involves the cows are slow to start lactation. They have reduced appetite and lower performance. At the same time, they are more susceptible to infections and problems which abomasal displaced and early culling.
Subclinical ketosis occurs most frequently in older cows, which have typically both higher mobilizing and higher milk yield then cows in first lactation. Usually, the incidence of subclinical ketosis is highest in cows, which are in high body score at calving (> 3.5). Such cows often have high milk production and low feed intake. Consequently they mobilize strongly.
* Subclinical means before clearly visible symptoms
Back to RYK's webpage in English
