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causes milk fever, but more so the fact that the cow's
system can take 24­48 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 25­30g magnesium per day. If a silage mineral
analysis is 0.15 per cent 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 per cent magnesium to
make up the deficit.
Potassium in Irish silages is typically between 1.8­2.4 per
cent. However, the dry cow requirement is only 0.52 per
cent. 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 per cent 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 per cent low in
copper, 69% low in selenium and 29 per cent 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
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.
If you answered
to one or more of the above,
your herd may be su ering from mycotoxin ingestion.
Poor quality?
High in ash content?
Or maybe none of the above?
Variable dry matter intake?
Is your herd
signs of:
Reduced milk or meat production?
Increased somatic cell count?
Poor conception rates?
Embryonic loss or calf abortion?
Cystic ovaries?
Blood in dung?
Inconsistent dung?
Leg and udder
Necrosis (rot) of the tail?
Is your forage:
For more information please contact your Alltech advisor on (01) 825 2244
European Bioscience Centre,
Sarney, Summerhill Road, Dunboyne, Co. Meath
Tel 1850 44 33 44
Is your silage quality
negatively impacting the
health and performance
of your herd?