Importance of milk fever
MILK FEVER IS THE MOST IMPORTANT NUTRITIONAL DISORDER AFFECTING TRANSITION DAIRY COWS
• Clinical milk fever affects around 4-9% of UK dairy cows2.
• Individual farms have clinical incidence rates of up to 60%3.
• For every clinical case another 3-6 cows in the herd could be suffering from subclinical milk fever4.
• 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.
EVERY DAIRY COW IS AT RISK OF MILK FEVER, MOST SUFFER FROM SOME DEGREE OF HYPOCALCAEMIA AT CALVING5
Every case of milk fever whether clinical or subclinical has consequences1,4:
• Lowered immunity.
• Slower rumen, abomasal and gut turn over.
• Reduced fertility.
• Reduction in milk yield.
Milk fever is associated with an increase in other early-lactation conditions4:
For more information download our guide to milk fever here.
Hypocalcemia In Dairy Cows
WHY DOES MILK FEVER OCCUR?
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 range5.
WITH THE ONSET OF LACTATION THERE IS A SUDDEN AND MASSIVE DEMAND FOR CALCIUM: AN EXTRA 80g PER DAY2.
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 urine5,8. 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 develops9.
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 parity4,5.
Risk factors that can help indicate individual cows or herds at greater risk include:
• Increasing lactations (any cow 2 lactations and above)2,4,5.
• 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.
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.
- Aim for lowest possible potassium in the diet of cows within 3 weeks of calving; this influences the incidence of milk fever.
- Minimise/ eliminate application of dung – it is high in K (potassium).
- Use straight nitrogen fertiliser on dry cow silage/grazing fields.
- Later cuts are generally lower in potassium.
- 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
or can also help to reduce risk – speak to your vet or nutritionist.
HOWEVER, THERE ARE FREQUENTLY SITUATIONS IN HERDS OR INDIVIDUAL COWS WHERE THERE IS AN INCREASED RISK OF MILK FEVER
- Older cows.
- High yielding.
- Previous case of milk fever in the cow/herd.
Supplementation with oral calcium such as Bovikalc® boluses helps to reduce the risk of milk fever and subclinical hypocalcaemia..