Time to focus more on minerals

16 September 2020

Taking a responsible and more precise approach to mineral supplementation can improve productivity and reduce costs.

Many farmers could improve profitability by paying closer attention to mineral nutrition according to Dr Liz Homer from Trouw Nutrition GB.

“Mineral requirements are a complex issue and it is vital that cows receive the right amounts,” she comments.  “However, in many cases rationing of these trace elements is not as effective as rations of, for example, energy and protein.  While diets will be refined to ensure the right levels of energy are fed to ensure requirements are met and that diets are cost effective, the same is often not true for minerals.”

Dr Homer says it is not unusual when auditing mineral use of farms to see farmers supplementing the diet with a range of mineral sources such as compound feeds, bagged minerals in the TMR of free access and as boluses or drenches.  Whilst this is not necessarily a problem, farmers and their advisors need to be certain that excess levels are not being supplied.

“Many supplementing products only contain three or four specific minerals which can lead to some minerals being under fed while others will be over fed. 

Dr Homer adds that as with the major nutrients such as energy and protein, the daily mineral requirements for a cow are affected by a whole host of factors including stage of lactation, actual level of production ,stage of pregnancy, disease challenge and the presence of antagonists which lock up or compete with other elements, such as molybdenum with copper.  This means that mineral inclusion levels need to be tailored accordingly as the consequences of getting it wrong can be considerable.

“In many cases we see more attention placed to mineral levels in fresh cow diets as they are yielding higher and need to reproduce.  The consequence can actually be that mid and late lactation cows risk being under-supplemented, especially as concentrates are trimmed back.”

Deficiencies mean cows will not perform to their potential, may not get in calf as quickly and will be more prone to a range of metabolic and health issues.  In most cases it is hard to pinpoint subclinical deficiency that contributes to chronic levels of problems, hindering health and performance.  Excess feeding can lead to toxicity and waste, as in most cases surplus minerals are just excreted, delivering no value to the animal and just increasing costs.


Adam Clay, Head of Technical at NWF Agriculture says that as a great deal is known about a cow’s requirements for minerals so it is possible to develop accurate diets.  There are however several factors that occur on a great many farms which conspire to mean diets are not as accurately balanced as they could be.

“The first is that detailed analysis of forages or water for mineral content is not usually carried out,” he says  “Concentrates and supplements are designed to supplement forages.  While the vast majority of farmers use a forage analysis of dry matter, energy and protein as the basis for ration formulation, very few have forages analyses for mineral content despite the facts that forage typically constitutes 50% of total dry matter intakes and that forages are a variable source of minerals. 

“The graph shows the extent of the problem.  A cow producing 30 litres and eating 11kgDM of grass silage will be facing shortages of seven key minerals unless supplementary feeds are effective at balancing the diet.

“Forages vary greatly from farm to farm, not just in overall mineral content but also the presence of antagonists.  In recent years drought and flooding will have had a direct impact on soil and forage mineral status.”

Mr Clay comments that many of the other primary ingredients used in dairy diets, including cereals and oilseeds, do not contain sufficient minerals to fully complement forages to meet the daily requirements of dairy cows.

“This means the diet requires additional supplementation, invariably from a wide range of sources and it is important that all sources are accounted for in formulating a diet.  Furthermore, it is important to take account of the relative availability of different mineral sources as this affects how well they are utilised by the cow.

“It is not unusual to have to take account of minerals from compound feeds, mineralised blends, free access minerals and blocks.  Furthermore, in some herds specialist supplements such as drenches and boluses may be used.  Unless the nutritionist is aware of all the sources that will affect total mineral supply, achieving a balanced diet will be very difficult and it is certainly a case that more is not always better.

He says the  primary sources such as compounds, blends and on-farm minerals will be formulated to a standard specification delivering against the requirements for a typical cow with typical intakes   The specialist supplements are typically used to meet a perceived deficiency or need for a particular mineral.

“A cost effective balanced diet must take full account of all sources and the decision on what to feed and when must be simplified to ensure each animal is receiving their requirements whilst not exceeding either legal maximums or approaching toxicity levels, particularly of potentially dangerous elements such as copper.

Mr Clay says that typically dairy compound is fed at an average of 4-5kg per day peaking at 8-10kg/day for peak yielding cows.  An additional mineral fed within the trough mix will still be required to ensure those cows on lower compound feed rates still meet their mineral requirements.  At the same time, that mineral needs to be balanced to ensure peak feed rate cows are not exceeding upper levels.  Using alternate copper sources will allows advisors to feed lower copper levels overall but with a higher availability, therefore reducing the risk of feeding excess.

Dr Homer believes farmers will benefit from increased precision when assessing mineral content in rations this winter, ensuring as much information as possible is collected on the mineral sources available.

“Don’t assume you can feed the same mineral as last year as your forages will be different and potentially cow requirements will differ depending on your attitude to target yield levels given current milk prices.

“Investing in a forage mineral analysis will allow your nutritionist to assess the most cost-effective way to ensure requirements are met.  In many cases, feeding a bespoke mineral will be more accurate, better for your cows and could reduce feed costs,” she predicts.