Get on top of your Magnesium Delivery

Get on top of your Magnesium Delivery

30 April 2021

Magnesium (Mg) plays a fundamental role in the cow throughout the whole season, but arguably, its most vital role is in the prevention of milk fever. Vanessa Lilly, Technical Sales Representative for Seales Winslow, highlights Mg's importance and the key considerations when deciding how you are going to deliver your herd's Mg this spring.

Mg plays an essential role in animal health. It is important for all things muscle and nerve-related, as well as enzyme activity in the animal.

Vanessa explains, "pre-calving, and early lactation is when a cow's Mg demand is at its highest".

It is during this time that the cow has a sudden increase in milk production, and therefore calcium (Ca) demand. A lack of Mg can result in milk fever (Hypocalcaemia). Mg plays a crucial role in Ca mobilisation from cows' bones. Mg (and therefore Ca) deficiency not only results in nerve dysfunction, which we see as restlessness, staggered gait and muscle tremors, but it also has an economic impact. It decreases milk production and increases medical costs. The potential cost of lost production during early and peak lactation outweighs the cost of prevention by far. The average wastage cost of milk fever being $1854/cow1, making it worth spending the extra dollar early.

The Dairy NZ Mg recommendation table below (Figure 1) shows a cow's dietary Mg requirement. For example, a crossbred cow requires a minimum of 16 grams (g) of Mg pre-calving.2

Mg levels in the pasture are typically very low over winter and during spring, and as it is not stored within the body, it is key that Mg is supplemented every day. Mg can be delivered in many different ways.

"Dusting in the water, in feed, such as mineral granules, or pellets, or via molasses lick blocks, are the typical ways of being able to deliver Mg to cows," Vanessa explains.

Whatever the option, there are a few things to consider when thinking about Mg:

  • What form of Mg is used? Oxide, sulphate and chloride all have different elemental levels and availability.
  • Consider how it is supplemented and wastage. Dusting paddocks means supplying more Mg than what is needed by the animal to allow for wastage.
  • Does every cow get what she needs every day? Using two points of Mg delivery can cover all the bases.
  • How practical is it for the farm infrastructure? Is it an effective use of time? And is it easy?

"Dehydrated molasses blocks are a great way to provide readily available Mg, without the hassle of handling dusty product," Vanessa says.

Seales Winslow Calver Max is a great option to provide high quality, highly available Mg in a safe and convenient way. Recent research has also suggested that a little and often' approach over the day is best where possible as it helps keep the blood Mg levels up throughout the day1.

Calver Max works to provide free access to Mg all day in a palatable way. The product not only offers two forms of readily available Mg, but it also contains trace elements and instantly available energy.

"The energy comes from the highly available sugar in the dehydrated molasses," Vanessa highlights.

"When used correctly, not only can this product aid in improving forage digestion and gut health but also provides 16g/day of Mg," Vanessa says.

Knowing best practice for supplementing Mg includes providing two different sources, Calver Max provides an easy and effective option A'.

visit, talk to your local Technical Sales Rep or visit your Farm Source Store.

Figure 1:Desired dietary magnesium concentrations and the quantity of supplementary Magnesium required (g/cow/day) for different sized animals (Dairy NZ, 2008)

1. Economic costs of recorded reasons for cow mortality and culling in a pasture-based dairy industry. American Dairy Science Association, 2018.
2.Dairy NZ, Farmfact 3-1 Magnesium Supplementation, 2008

Article and images supplied by Seales Winslow.