Getting magnesium supplementation right over spring is likely to have the greatest effect on reducing the incidence of metabolic problems.
The cow is totally dependent on what magnesium is supplied in their daily diet. The magnesium content of spring grass is relatively low and only a small percentage of this is absorbed by the cow. One of the main factors affecting availability of magnesium is herbage potassium levels. High pasture potassium level causes significant decline in absorbable magnesium, particularly in spring when herbage magnesium is at its lowest.
Start supplementing with magnesium daily for 3-4 weeks pre-calving.
The best way to achieve the required dietary magnesium concentration pre-calving is to add 60 grams Mag C or Mag S/cow/day into the water supply and dust pasture/silage with 50-70 grams Mag Oxide/cow/day as well.
If the herd is experiencing more than a 3% incidence of milk fever despite sufficient magnesium supplementation then colostrum cows can receive calcium supplementation via lime flour at 200g/cow/day dusted on the break. Lime flour can continue to the milkers at 100g/cow/day for the first 6 weeks after calving if required.
To avoid metabolic problems:
- Maintain adequate dry matter intakes over the spring period
- Supplement with sufficient magnesium
- Avoid grazing potassium rich effluent paddocks with springers and colostrum cows
- Avoid excess applications of potassium rich fertiliser during the months of June - October.
- Blood test mature cows on day 3-4 of the colostrum period for metabolic profile.