While clinical milk fever is generally easy to identify and can be treated it is very much the tip of the iceberg as signiﬁ cant losses arise from the sub-clinical form.
At the tip of the iceberg it is estimated that 5-7% of cows are affected by clinical milk fever, below the water, a far higher proportion are likely to be suffering sub-clinical milk fever which is more difﬁcult to identify and economically more damaging.
Milk fever is caused by the increased demand for calcium at calving resulting from the onset of milk production. The result can be a rapid decline in blood calcium levels. If levels cannot be maintained, either from the diet or the mobilisation of calcium stored in the bone, milk fever results.
Typically up to 50% of third lactation + cows will have a degree of clinical or sub-clinical hypocalcaemia. Incidence rate of clinical cases will vary from 1% to up to 80%. This is an expensive disease if production loss, increased culling, delayed conception and other disease factors are taken into account. Our own studies indicate a cost of £450 for a clinical case of Milk fever and £74 per subclinical case. Clinical cases may result in the loss of the animal in extreme situations or complete recovery in mild cases.
At a 20% incidence rate a typical 200 cow UK herd could be losing around £18,000 per year alone from milk fever, so effective prevention strategies should be a priority.
Prevention starts with good basic management and reducing stress in dry cows. Avoiding overcrowding, reducing unnecessary changes in groupings and ensuring sufﬁ cient trough space will all help.
Avoid high calcium feeds
The diet is key. Get this right and the incidence of both clinical and sub- clinical milk fever can be reduced. Feed only good quality forages free of moulds and mycotoxins and avoid high calcium feeds like grass silage, beet pulp and lucerne, especially in the last three weeks before calving. Ration guidelines to help reduce the incidence of milk fever include:
- 12-14kgDM intake.
- 50% NDF.
- 125MJ fed (adjusted for breed / weight of cow) three weeks pre calving – if one dry group target 120MJ through the whole dry period.
- Feed high quality protein sources to deliver 1200g of Metabolisable Protein.
Milk fever is largely preventable with good controls in place, but there is also a wide range of solutions available to ‘solve’ the problem of calcium metabolism.
These include approaches such as oral drenching with easily absorbed calcium immediately post calving. Then there are full and partial DCAB diets as well as speciﬁc low potassium and low calcium diets which all inﬂ uences the metabolic balance in the cow. Some are easy and quick to implement, others less so.
With such an enormous range of commercial products designed to help it is very easy to get confused when choosing a solution. Independent advice will steer you towards the optimal solution by assessing the incidence and history of milk fever together with proper analysis of the environment and feedstuffs can the best solution be determined. Our consultants are well-placed to provide an impartial assessment of the most effective way to reduce the losses from clinical and sub-clinical milk fever in your herd.