Milk fever
Every case of milk fever whether clinical or subclinical has consequences1,2
Importance of milk fever
Milk fever is one of the most important nutritional disorders affecting transition dairy cows.
- Clinical milk fever affects around 4–9% of UK dairy cows3
- Individual farms have clinical incidence rates of up to 60%4
- For every clinical case another 3–6 cows in the herd could be suffering from subclinical milk fever2
- Clinical cases indicate there is a level of subclinical milk fever in the herd, however herds can also have subclinical milk fever without clinical cases
Why milk fever occurs
99% of calcium in the cow’s body is stored in the bones and teeth. The rest circulates in the blood and needs to be maintained within a narrow range.5 With the onset of lactation, there is a sudden and massive demand for calcium – an extra 80 g per day.3
The cow can adapt to this change by drawing on her own calcium reserves (bone and tissues), improving absorption from the diet and by reducing losses in the urine.5,6 This adaptation occurs with the help of the cow’s calcium homeostatic mechanisms.
There is a balance between lactational calcium demands and the ability of a cow to mobilise her own calcium reserves to meet this demand.
The cow’s ability to maintain this balance and meet demands influences whether or not milk fever develops; in those cows unable to maintain this balance, milk fever develops.7
Which cows are at risk?
All cows calving are at risk of milk fever, and most have some degree of low blood calcium (hypocalcaemia).5 However, risk does increase with age and parity.2,5
Risk factors that can help indicate individual cows or herds at greater risk include:
- Increasing lactations (any cow 2 lactations and above)2,3,5
- High yielding cows
- Previous history of milk fever
- Body condition score >3.5
- Grass-based diets/forage or diet high in potassium (K)/high DCAD
Supplementation with oral calcium such as Bovikalc® boluses helps to reduce the risk of milk fever and subclinical hypocalcaemia.
Managing milk fever
Clinical and subclinical milk fever to a large extent can be prevented through transition cow dietary management and nutrition.
-
Plan dry cow forages in advance
-
Later cuts are generally lower in potassium
-
Use straight nitrogen fertiliser on dry cow silage/grazing fields
-
Minimise/eliminate application of dung – it is high in K (potassium)
-
Aim for lowest possible potassium in the diet of cows within 3 weeks of calving; this influences the incidence of milk fever
-
Keep grazing tight – tops of stems have more potassium than the bottom
-
Calve cows down in the right body condition (BCS 2.75). Fat cows are more likely to get milk fever and have calving difficulties, ketosis, etc.
-
Ensure that there is a good magnesium supply to dry cows (involved in calcium absorption); this usually means either a mineralised dry cow roll or specific dry cow mineral
-
Feeding small amounts of certain salts such as magnesium or ammonium chloride can also help to reduce risk – speak to your vet or nutritionist
Every case has consequences
Milk fever is associated with an increase in other early-lactation conditions.2 Every case of milk fever whether clinical or subclinical has consequences1,2:
- Lower immunity
- Slower rumen, abomasal and gut turnover
- Reduced fertility
- Reduction in milk yield
-
1. Mulligan, et al. Irish Vet J. 2006;59(12):697-702.
2. Houe, et al. Acta Vet Scand. 2001;42:1-29.
3. Husband. In Practice. 2005;27:88-92.
4. Bovine Medicine. Diseases and Husbandry of Cattle. 2nd edition. eds: Andrews, et al. Major metabolic disorders. Eddy RG. Blackwell Science Ltd.
5. Degaris, et al. Vet J. 2009;176:58-69.
6. Constable, et al. WBC Chile 2010. Monitoring DCAD Diet in Dairy Cattle.
7. Sampson, et al. Vet Therapy. 2009;10(3):131-139.