Mineral supplementation is a crucial aspect of the dry cow period to help with body condition score (BCS), calving down and the overall health of the calf.
Inadequate mineral supplementation during the dry period poses the greatest threat to cow health, but it also has a knock-on affect on the newborn calf’s health.
The dry cow needs to be supplemented with pre-calving minerals for six weeks before calving, and the correct feeding level should be offered.
Cow health problems from inadequate mineral supplementation are as follows:
- Clinical and subclinical milk fever;
- Ketosis;
- Retained cleanings;
- Low dry matter (DM) intake;
- Displaced abomasum;
- Fertility issues.
It is crucial to feed minerals in order to avoid these issues, but it is equally important that cows are in the correct BCS at both drying-off and, most importantly, calving.
Mineral supplementation
Typically, mineral specifications are formulated to a 120g/cow/day feeding rate and if they are getting dusted onto silage, it is advised that the minerals are spread twice daily, with 60g/cow in two feeds.
Feeding minerals twice daily ensures that intake is controlled and that all of the cows have access to the minerals, and is especially important when there is not enough feed space in the shed.
When it comes to preventing milk fever, magnesium (Mg) is the key mineral and the cow will require about 20-25g/cow/day, which is the equivalent to about 17-21% Mg in the mix for a 120g feeding rate.
Trace minerals and vitamins such as copper, selenium and zinc should all be fed at least six weeks pre-calving to achieve adequate levels for the calving period.
There should be enough vitamin D of at least 120,000 units/kg in the mineral supplementation to help prevent milk fever.
The daily mineral and trace element requirements of your typical dairy cow pre-calving at a typical feeding rate of 120g/head/day should be as follows:
What you see on the label What the animal gets Major elements Calcium 0% 0g Phosphorus 0-4% 0-5g Sodium 15% 18g Magnesium 17-21% 20-25g Trace elements Copper 4,800mg/kg 400mg Selenium 60mg/kg 5mg Iodine 600mg/kg 50mg Cobalt 120mg/kg 10mg Zinc 6,000mg/kg 500mg Manganese 1,200mg/kg 100mg
If there is a history of health issues on the farm such as milk fever cases at calving, farmers should test the mineral content of the forage.
High potassium (K) silage can often be the cause of milk fever problems and farmers should make sure cows that are on the point of calving are fed low potassium (K) forage (under 2.2%).
Before feeding any minerals, farmers need to check that the mineral specification meets the herds requirements; the feeding rate is correct; and that the minerals are fed twice daily.