Home / Dr. Carleys Blog /Comparison of Synergy with NRC guidelines for a 500kg healthy adult horse at maintenance.
Comparison of Synergy with NRC guidelines for a 500kg healthy adult horse at maintenance.

The National Research Council (NRC) guidelines are the industry recognised standard for recommended daily rates of nutrients for horses. All grazing, forage and browse will contain various amounts of vitamins, minerals, and other essential nutrients, but very often due to modern farming techniques, pasture management, etc, many of these nutrients can be deficient. When formulating a balancer (to ‘balance’ against this forage), Thunderbrook take into account the levels of such nutrients in a typical UK forage.

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Some nutrients are typically in short supply and are important additions to a balancer (such as copper, zinc, magnesium and selenium) whereas others are often supplied in abundance in typical forage and to over supplement could be detrimental (for example iron and manganese). Hence, it would not be sensible to formulate a balancer that meets 100% of the NRC nutrient requirements just from the balancer alone, as the nutrients provided from forage which makes up the bulk of the horse’s diet also need to be taken into account.

Synergy meets the full daily requirement for the main vitamins and minerals, according to NRC guidelines, when fed at the recommended daily rate alongside forage. Vitamins and minerals are supplied in Synergy through those naturally sourced from the ingredients (linseed, nutritional yeast etc) and from those added separately (labelled and declared as ‘additives’ under EU legislation). The additives have to be declared by law, but the nutrients supplied through the natural ingredients do not have to be declared on the label. This is simply because they are harder to quantify as there is natural variation from batch to batch. The table below gives more information than that what is legally required on a feed sack label. It includes to the best of our ability the nutrients provided from the ingredients as well as the separately added nutrients.

The main vitamins and minerals to balance against average UK forage are highlighted in red in the table below. These are the key vitamins and minerals (copper, zinc, magnesium and selenium) that can be in short supply in average UK forage.

Some minerals are not added to Synergy (such as iron and manganese) as they are rarely ever found to be lacking in the horse’s forage and excess supplementation is considered potentially harmful. For example, the 400mg of iron per day according to NRC guidelines in the table below will be obtained from eating just one or two kilos of average hay. The levels of iron and manganese in Synergy are from the natural ingredients only (linseed, nutritional yeast, etc). Other minerals such as selenium are toxic when fed at higher levels. As selenium levels can be low in forage, but rarely ever completely lacking, we include selenium at slightly under the NRC level to compensate, and ensure we avoid toxicity problems.

Some balancers contain copper and zinc at many times the NRC recommended daily rates. Synergy is formulated to meet the NRC requirements, but not at multiple concentrations higher. This is for two reasons. Firstly because the NRC guidelines are the most researched data available. Claims that higher levels of copper and zinc are required are not backed up with robust scientific research and peer reviewed papers. Secondly because the European Legislation on feed additives has maximum limits set for minerals such as copper and zinc, to avoid toxicity. Adding copper and zinc in Synergy at multiple concentrations higher to the NRC guidelines could result in toxicity if the horse’s forage is already high in copper and zinc (and occasionally this can be the case).

Calcium, phosphorus and potassium are always found in forage and a horse’s diet is rarely short of these minerals, so again they are included at levels to balance average UK forage, and each other. Similarly, sulphur is found in grass (average 0.2%). A 500kg horse eating 10kg dry weight of grass will consume 20g of sulphur which is higher than the NRC guideline figure, and hence we do not include additional sulphur in Synergy.

Sodium and chloride are the constituents of basic ‘salt’. We do not include salt in Synergy as this would compromise the shelf life of the product (and it is also a cheap ingredient that can easily be added separately). Cobalt is not included as there are legislative requirements regarding the addition of cobalt to animal feeds. The level of cobalt quoted in the table for Synergy is that found from the natural ingredients. We add Vitamin B12 instead (which is a vitamin made from cobalt).

If you have any questions about our nutritional analysis, please feel free to call our nutritional helpline to discuss further.

This blog is part of an archived library.  These blogs were originally written from 2009 through to 2014, so some are over a decade old (apologies the exact dates have been lost on website updates).  Research and informed opinions are a constantly evolving stream of work, so there will always be updates required to any older blog post, research paper, etc.  For the latest information, please email [email protected] or telephone 01953 797050 for nutritional advice.  Thank you. 

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