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Dry cow minerals that go to work, not to waste.

Dry cow minerals that go to work, not waste

Dry cow minerals that go to work, not to waste.


Successful transition from the dry period into lactation is one of the most critical moments in a dairy cow’s lactation. It will have a direct impact on milk production, cow health and reproductive performance during the subsequent lactation.

To achieve a successful transition, the management and nutrition of dry cows needs to be right. The success of the transition revolves around four key pillars: Body condition score, nutrition, minerals and management.

During the dry cow period, these four pillars will lead to smooth, stress-free calving and set their herds up for successful lactation by reducing metabolic issues around calving, including milk fever, retained placenta, displaced abomasum and ketosis.

As previously mentioned, one of the four pillars relates to correct mineral nutrition. Dry cows should be fed a dry cow mineral for the duration of the period (ideally between six to eight weeks). This is to ensure there is a good reserve of minerals built up, allowing the cow to calve down without any issues and continue into the lactation to follow.

Testing silage

Most Irish silages do not supply the required amount of minerals to get the cow through the dry period. As a result, these minerals need to be supplemented. If you have not already done so, test your silage for minerals.

It is important to note that the mineral status of our soils and forages varies tremendously from farm to farm and year to year. The simplest and most accurate way of knowing the mineral status is by testing the forages being fed to cows, whether it be grass, grass silage, maize or wholecrop silage. Once found, informed decisions can be made on the most effective way of supplementation.

To date, many of this year’s silage analyses are showing a deficiency in phosphorus and an excess supply of potassium due to a high level of soluble nitrogen, caused by high fertiliser- and slurry-application rates.

Managing milk fever

When it comes to major mineral nutrition, it is essential to establish a good basis for the control of milk fever and sub-clinical milk fever. Milk fever is known as the ‘gateway disease’ because it leads to many other complications, such as retained cleanings and displaced abomasum. Research shows that where milk fever is relatively well-controlled, approximately 33% of cows experience sub-clinical milk fever.

The risk of milk fever reduces if cow BCS is monitored and controlled in late lactation and throughout the dry period. Cows should be dried off between BCS 3–3.25, with this BCS maintained throughout the dry period. Cows with both too high and too low BCS are shown to have an increased risk of milk fever.

Clinical milk fever is usually easy to detect. Sub-clinical milk fever, however, is often difficult to see and can often go unnoticed. This, in turn, can increase costs, as it affects more cows and leads to varying metabolic disorders, such as retained cleanings, metritis, mastitis and ketosis.

The increase in demand for calcium around calving and the transition period presents a significant challenge for a cow’s system. The cow’s normal reserve pool of calcium is about 2.5–3.5g and cows can only afford to lose approximately 50% of this pool before a hypocalcaemia crisis is initiated. With a single litre of colostrum requiring 2.3g of calcium, it is easy to see how a cow can quickly become calcium deficient.

It is not so much the sudden demand for calcium that causes milk fever, but more so the fact that the cow’s system can take 24–48 hours post-calving to become fully functional. It is this time lag that causes the cow to drain calcium from her plasma pool, and as this reserve decreases, so too does the cow’s blood calcium status, possibly bringing about a case of sub-clinical or clinical milk fever.

In order to avoid this, it is critical that mineral supplementation continues up until the point of calving and an adequate post-calving mineral is also supplied.

Major mineral requirements

Magnesium is a crucial major mineral in relation to the control of milk fever. Magnesium is necessary for the metabolism and absorption of calcium within the cow around calving. Throughout the dry period, a cow needs between 25–30g magnesium per day. If a silage mineral analysis is 0.15% magnesium, a cow eating 11kg dry matter intake (DMI) during the dry period will take in 1.65g of magnesium from silage. As a result, the mineral supplement will need to supply at least 24g of magnesium. If the feed rate of the mineral is 120g per head per day, there needs to be a minimum of 20% magnesium to make up the deficit.

Potassium in Irish silages is typically between 1.8–2.4%. However, the dry cow requirement is only 0.52%. Potassium interacts closely with magnesium, locking it up in the rumen, which can slow down the absorption and mobilisation of calcium, leading to milk fever. With sufficient magnesium supplementation, the typical levels of potassium can be managed. If potassium is greater than 1.8% in silage, alternative measures need to be taken, such as introducing Cal-Mag or sweetened Cal-Mag.

Unless you are following a DCAD diet program, grass silage can supply the calcium required during the dry period. This ensures that the cow mobilises calcium reserves within her bones and bloodstream, reducing the risk of milk fever.

Trace minerals during the dry period

Trace minerals, or micro minerals, play a massive role in supporting immune function, fertility and production of dairy cows. Throughout the dairy cow’s cycle, calving is the most stressful period on the immune system. It is important that throughout the dry period, the cow can build up the necessary amount of trace minerals to allow her to draw from her reserves when she calves down. Irish grass silages have been shown to be 63% low in copper, 69% low in selenium and 29% low in zinc (Rogers and Murphy, 2000). As a result, supplementation is essential.

Important trace minerals:

  • Selenium: Works with Vitamin E, acts as an antioxidant and helps support cow and calf immune function. Calves fed protected selenium in the form of Sel-Plex® are well-developed (heart, lungs, skeletal) and have a good suckling ability. Sel-Plex sets up the cow for the lactation to come and reduces the incidence of high somatic cell count (SCC) and mastitis in the following lactation.
  • Copper: Copper is involved in the creation of red blood cells. In its organic form, such as Bioplex® copper, it is key to maintaining successful immune function pre-calving and into the lactation to follow. Bioplex copper also plays a key role in reproduction and hoof health as the cow begins the lactation cycle.
  • Zinc: The trace mineral that influences udder and hoof health in dairy cows. Zinc supplementation is essential at all times of the year as it helps to keep SCC under control, reduces incidences of mastitis and helps to maintain the hardness of the hoof. During the dry period, zinc in its protected form is key to supporting immune function.
  • Iodine: Low dietary iodine intake during pregnancy has been associated with an increased incidence of small and weak calves, increased incidence of goitre, decreased resistance to hypothermia, decreased survival and low immune function. In the following lactation, cows recycle poorly, which means that iodine is not stored in the body and so must be supplied in the diet.

On many farms throughout the country, producers are using minerals containing inorganic salts of trace minerals, such as sodium selenite and copper sulphate. However, this form of trace mineral is not what the animal has evolved to use. The soil contains inorganic minerals, which are then taken up by the plant (i.e., grass) and converted to organic forms of minerals. The animal then eats the plant containing minerals in this organic form. The animal cannot store inorganic minerals, so they are not reserved for times of stress, such as calving or disease.

Feeding trace minerals in their organic form — such as Bioplex copper and zinc and Sel-Plex, an organic form of selenium from Alltech — leads to these minerals being absorbed at higher levels, stored and utilised by the animal. This helps to build the cow’s immune system, supports her during stressful times and helps overall cow performance.

Using proven technologies as part of a dry cow nutrition programme generates a higher return on investment, benefitting both cow performance and farm profitability. Many farmers across Ireland are now seeing a positive response in their herds from using Bioplex and Sel-Plex in their dry cow mineral.



To discuss options for implementing a successful dry cow programme this season, get in contact with Alltech today.