In the second of our new feature we concentrate on MILK FEVER


Average incidence of milk fever is typically 5 cases per 100 cows per year. This year there have been instances of almost every mature cow showing signs of milk fever.

Milk fever can also trigger off other problems such as displaced abomasums, retained cleansings, mastitis and ketosis. Many of these problems can be cumulative so the cow can get all the conditions with a severe financial penalty occurring.

Why should milk fever be a problem? You will be aware that milk fever is a result of low calcium availability at calving. However, the evidence currently indicates that magnesium chloride, sulphur and sodium phosphorus can all have more influence on milk fever than calcium levels. The real culprit appears to be POTASSIUM with its antagonistic (locking up) effect on magnesium and other effects on the cows ability to mobilise calcium from bones and its absorption from the digestive tracts.

Potassium is very high in a lot of early first cut silage. (This link is well established with grass staggers and magnesium shortages). Grass silages can easily be 4% in potassium. If this is the single forage then it is impossible to get dietary levels to the target max of 2%. Autumn grass is also low in magnesium and high in potassium producing similar results.

Given below are some guidelines to help you manage milk fever. Discuss the various options with your vet, as each farm circumstance will vary.

  • Have an established dry cow programme maximising intakes and using appropriate mineral, especially magnesium or dry cow roll. This stimulates appetite and will reduce milk fever. GP Feeds Dry Cow range meets these requirements.
  • If possible test forages available. Restrict any forages high in potassium. Maize silage can be lower as can wholecrop but these are also increasing in potassium levels. If milk fever is a problem, make big bales in a field that has more traditional grasses and receives low amounts of fertiliser, use this forage just in the dry period.
  • Be careful of too high or too low calcium levels in the diet. Legumes, milking cow minerals, protected fats and Sugarbeet can be high in calcium but it is very difficult to get calcium levels low enough to stimulate calcium absorption. Cows have a requirement for calcium and too low a level in the diet at calving can trigger problems.

Monitor when the milk fever occurs.

  1. Pre-calving cases can be caused by low calcium in the diet and usually respond to extra calcium.
  2. On the day of calving, the cow cannot mobilise calcium from reserves quick enough. This is linked to potassium levels and other minerals. At calving or just before calving, cows should be put on a diet with much higher calcium levels. They should not stay on the low calcium dry cow diet.
  3. Two to six days post calving can be linked to low calcium in the diet and also linked to phosphorus levels.

Use of DCAD (Cation Anion Difference)

Dietary Cation Anion Difference – this approach is used in the US but is not an easy option. Basically Cations such as potassium and sodium create a blood stream that is alkaline (urine PH8) (note the problem of high potassium). Anions such as sulphur and chloride create acidity in the blood stream (urine PH 6.5). This acidity improves the re-absorption of calcium from the bones and makes it more readily available. Values are calculated in meg / 100 and a negative figure of –10 to –20 is the target. After calving a high positive figure can help intakes but more of this in a later article. High levels of calcium are fed (about 150 gms / day) and with this system without the risk of milk fever. Anionic salts are added to the diet until the urine PH it at 6.5. This approach needs to be under the supervision of a competent nutritionist and great care should be taken. The addition of magnesium chloride about 7 days before calving can help as a result of increasing magnesium levels and the chloride does act as a DCAD

Use of calcium paste or gels at calving. Better products are now available in the US with improved absorption so keep an eye out for these.

If you want help with formulating dry cow diets to minimise milk fever give us a ring 01948 661602.