As autumn approaches and the grass growth declines it is time to think about the cows that are approaching calving. These animals can often be forgotten during the summer months and taken for granted as the nights draw in, even though the calving period is the most risky time for cattle. One thing worth a thought or two is milk fever, a common condition that can have a serious impact on a seasonal calving herd.
It is estimated that each case of milk fever can be costing around £250 and it is thought that around 4-9% of the UK’s dairy cows are affected by clinical milk fever per year, with some farms reaching up to 60%. Subclinical milk fever, where symptoms are not visible, but the cow and its productivity are affected, is present in up to 39% of dairy cows.
Cows that have clinical or subclinical milk fever are more likely to require assistance at calving, retain their fetal membranes after calving, suffer from metritis and endometritis and go on to have a left displaced abomasum. Milk fever is one of the most important nutritional disorders affection transition cows and is a preventable condition, so it is not something to ignore.
August to October sees increased incidence of milk fever so it should be high on the list of considerations for an autumn calving herd. Milk fever can be difficult to predict- indeed some cattle without signs of the condition are still suffering from low levels of calcium (subclinical milk fever) and go on to have side effects associated with the disease itself. The condition is more likely to affect older cattle, as their ability to mobilise skeletal calcium decreases with age. With the onset of lactation there is a sudden increase in demand for calcium – an average extra 80g per day. Cows can draw on their own calcium reserves (bones and guts) to try and meet this extra demand. However, if they are unable to meet their calcium demand, milk fever develops. The disease can largely be prevented by transition cow nutrition and management, however there are times when cows are more at risk. This includes, older cows, high producing dairy cows and those with body condition score over 3.5.
Clinical signs of milk fever include lethargy, muscle tremors and a head twisted round onto the body of a down cow. Clincial milk fever needs to be treated promptly with calcium to prevent the signs progressing to death of the animal.
The risk of milk fever is easily and successfully reduced by supplementing the cow with oral calcium just prior to calving. This must be done using the correct balance of calcium salts so that they are absorbed by the body in a way that maintains the calcium level at the critical period to reduce the risk of milk fever occurring. Bovikalc® boluses from Boehringer Ingelheim contain calcium chloride and calcium sulphate to provide a quick and sustained release of calcium, whilst also having an acidifying effect that helps the cow to mobilise her own calcium reserves. Reducing the risk of milk fever before it occurs could help reduce the other conditions associated with the milk fever to make the calving season healthier and more profitable.