With less than a month to go before the main calving season commences, farmers should be feeding pregnant animals dry cow minerals.

These minerals supplement what the cows consume in their diet, for example silage.

There are lots of products on the market and it gets confusing comparing all the different types. By right, the type of dry cow mineral required depends on the mineral analysis of the silage.

In the absence of this, most farmers will just buy an off-the-shelf mineral. The key ingredients are magnesium (Mg) and phosphorus (P).

Low inclusion rates of each will lead to cheaper minerals to buy, but you will have to feed more of them, so it’s really a false economy.

Standard feeding rates are 120g per cow per day, so compare different specs to this common feeding rate.

Requirements

The dry cow requires between 20g and 25g Mg per day before calving. If the label says there is 20% Mg in the mineral mix and you are feeding 120g per day, then the cows are getting 24g Mg per day.

The next big one is P. Not all minerals will have P included, but most cows need around 4g/day before calving. Minerals with high P levels are generally more expensive.

Trace elements

Trace elements such as copper (Cu), selenium (Se) and zinc (Zn) are also important. For Se, the target is for 5mg or 6mg per day pre-calving. If it says there is 50mg on the label and if 120g per day is fed, then the cows will be consuming 6mg per day.

Iodine is a tricky one. By right it should not be fed at more than 12mg per cow per day, but if the forage is very low in iodine, then more will have to be supplemented in the minerals.

Iodine deficiencies are common in some farms and result in slow calvings and weak calves.

Vitamin D is also important and should be included at a rate of at least 120,000 units per kilo of mineral. This is important in the prevention of milk fever.

Also important in the prevention of milk fever is low potassium (K) levels in silage. If silage is high in K, then this silage should not be fed to cows close to calving. Ideally, silage should be less than 2% in K.