Minerals need to move up the nutritional agenda as dairy farmers strive for greater efficiency
17 February 2020
Laura Drury argues that minerals have consistently taken the back seat to energy, protein and other macro-nutrients but adds that imprecise mineral nutrition is having a significant impact on short-term and long-term performance as well as a large effect on the environment.
“Effective mineral nutrition, as with any other nutrient is about balancing animal requirements with dietary supply in the most efficient way. Feed too little and performance can be affected. With minerals this will impact on milk production, fertility, lameness, immune function and consequently longevity.
“Feed too much and the excess will generally be excreted, increasing costs for no benefit and potentially causing environmental issues. While farmers and nutritionists also appreciate the importance of considering different sources of energy and protein, the impact of different sources on minerals is less well understood but the benefits of optimising sources are considerable.”
Laura explains that sources of trace minerals vary in two major ways. The first is their bioavailablility, which is the proportion that is absorbed and available for use by the animals. The second is the effect they have on rumen function and also the availability of other nutrients in the diet.
Traditionally the form of minerals added in animal feeds has been inorganic salts such as copper sulphate, zinc oxide and manganese oxide. Whilst these tend to be the cheapest sources of trace minerals, research has shown sulphates to have negative effects on rumen function, whereas oxides have been shown to have very low bioavailability, even less so than sulphates Both of these aspects limit optimal animal health and performance within animals.
“Small amounts of trace elements are required for proper functioning of rumen micro-organisms, which can be provided via the basal diet such as forage, however added inorganic sulphate sources included in supplementary feeds are also highly soluble in the rumen which greatly compromises not only their efficacy, but also rumen function. Due to their high solubility at rumen pH levels, the free metal can bind to antagonists meaning less is available for absorption. In addition, they can tie up phytate which is a natural form of phosphorus in plants. The consequence is an increase in the phosphorus excreted by the cow which is an environmental problem.
“It is worth pondering that sulphate trace minerals are commonly used to kill microbes in footbaths, so what are they doing to the microbes in the rumen?”
Organic trace minerals commonly known as chelates have been used to partially replace inorganic minerals for some time now. In these products, the mineral is bound to amino acids or proteins, making them more bioavailable to the animal. While they have greater bioavailability, they are expensive, meaning there is a reluctance to include high levels of them in many mineral supplements.
“A recent innovation to enter the UK market are IntelliBond hydroxy trace minerals. As a cost-effective alternative to inorganic minerals, IntelliBond helps to deliver improved bioavailability whilst mitigating the negative impact that inorganic minerals have on rumen function and nutrient utilisation efficiency.
Laura says that these benefits have been shown to have a positive effect on milk production economics.
“For optimal milk production we need a rumen that is efficiently digesting fibre. If we increase fibre digestibility, we can increase milk output. Research at Michigan State University shows that each 1% increase in NDF digestibility can increase milk output by 0.25-0.3kg.
“Research (see graph) has shown that complete replacement of sulphate trace minerals with IntelliBond hydroxy trace minerals can optimise NDF digestibility by up to 3.4%, enough to increase yields by over 0.75litres/day and leading to a positive return on investment.
Laura points out that as forages and commonly used feed ingredients have low mineral contents, many mineralised compound feeds have high mineral contents to ensure an adequate supply to meet requirements. In many cases there will be a high proportion of inorganic minerals in an attempt to keep cost down.
She says there is also evidence to show that if too much mineral is supplied that cows become less efficient at absorbing the minerals and that retention by the cow is better where the supply in the diet is less from a quality source.
She says the objectives of a mineral strategy should be to meet the requirements of the cow, using the least amount of quality supplementary minerals to maximise absorption while minimising the negative impacts of other nutrients such as fibre digestion and vitamin stability.
“The danger is that in many cases you may be supplying in excess of requirements. As the performance and cost benefits of getting mineral nutrition as precise as possible are considerable, it is important to take a closer look at mineral supply and sources”.
“The starting point should be to understand the contribution from all the feeds available, and this must include water especially when it is supplied from a borehole.
“Get a mineral analysis of your water carried out and have forages analysed for mineral content regularly too. This will be especially important this spring as the wet winter and widespread waterlogging will potentially cause reduced soil mineral availability and reduce the concentrations in forages.
“Armed with this information you will know the mineral supply from forages and can begin to build a cost-effective diet in the same way as you would for energy and protein.
“As you add supplementary minerals, don’t just go for the cheapest source. Most of the minerals in forage and straights will be soluble sources and also vary widely in their availability so feeding hydroxy minerals in supplements will be a more efficient way to improve precision of supplementation.
“As an example, complete replacement of inorganic zinc and copper in a premix with half the level of IntelliBond Z and C respectively which have approximately double the bioavailability of inorganics would cost less than £1 per cow more per year. Using the latest Trouw Nutrition rationing model for IntelliBond, the improved NDF digestibility will allow an extra 0.5 litres/cow per day, worth around £45 over a lactation.”
Laura also says that when calculating the mineral supply of the diet it is essential to include the supply from blocks, drenches, lick buckets and boluses as they can be significant contributors.
“With farmers focussing more on efficiency and driving productivity in the expectation of fairly static milk prices, looking more closely at the sources and overall supply of minerals will be a good starting point. Minerals have a significant impact on multiple functions in the cow. Get nutrition right and production and fertility will improve while disease incidence and costs can be reduced. Furthermore, the environmental impact of dairy farming can be improved.”