The importance of testing forage for laminitis prone horses
It’s the time of year when, as a nutritionist, I spend proportionally more time speaking about laminitis either giving advice via the Dengie Feedline or during talks at client evenings.
For horses that have restricted grazing, the reliance on conserved forages increases and one of the common questions we have is “how do I know if my forage is suitable for my laminitis prone horse?”. In addition to this, there are some perpetual myths regarding the suitability of certain forages for laminitis-prone individuals that cause concern. One of the most common is that last year’s hay is safer than this year’s hay which isn’t always the case. My answer to these queries is always the same – if you can, get your forage tested.
What affects the nutritional quality and suitability of forage?
Environmental conditions during growth and at the time of harvest, the type of grass and the age of the plant at the time of harvest all have an impact on the nutritional profile of forage. You can’t tell by looking at a forage what it will supply, particularly in relation to its sugar content, and so testing is helpful. For those concerned about laminitis-prone individuals, levels of non-structural carbohydrate (NSC) in a forage are a key factor to consider. This is an analytical term and is the sum of water-soluble carbohydrates (WSC) and starch added together. Water-soluble carbohydrates are simple sugars plus fructan which is the storage carbohydrate for grass. The current consensus is that less than 10-12% NSC on a dry matter basis should be aimed for, but for some individuals this may still need to be lower. In addition to the NSC content the amount of Digestible Energy (DE) in the forage is also of concern as keeping horses at a healthy weight is half of the battle when it comes to managing laminitis risk.
For many years now Dengie have offered a forage analysis service where we send forage to an external laboratory for testing and translate the results into practical information and advice for horse owners. Recently I re-named the different tests so it’s much easier to identify which ones to carry out to determine if a forage is suitable for a laminitis-prone individual. As harvest is in full swing it seemed like the ideal time to review the results from the last 12 months.
Types of forage tested
Historically we have always tested a greater number of hay samples than other types of forage. Increasingly though, we are testing more forage that we would describe as wrapped hay rather than haylage. Of the wrapped forage samples that have been submitted in recent years, only around 20% of them have been true haylages by which we mean fermentation has taken place. We are now defining the rest as wrapped hay as they have a dry matter greater than 65% and so little or no fermentation has taken place. This means that nutritionally they are more like hay than haylage even though they are wrapped in plastic.
Digestible Energy
The forages tested supplied very similar levels of DE with an average of 9.8MJ/kg and ranging from lows of 9.1MJ to highs of 10.5MJ. A 500kg horse consuming hay to appetite, which would be approximately 12.5kg dry matter, would consume 122.5MJ based on the average. A 500kg horse at rest only requires around 70MJ DE to maintain weight and so it’s no wonder that ad-lib hay is likely to result in weight gain based on these results.
Water-Soluble Carbohydrate
The percentage of water-soluble carbohydrates on a dry matter basis for the forage samples tested can be seen in the graph below. The tests were conducted using wet chemistry techniques. In a true haylage where some fermentation occurs, the level of water-soluble carbohydrate can be lower than hay as it is the sugar that is fermented to create volatile fatty acids (VFAs). However, a lower sugar content needs to be considered along with other key factors such as the energy level in the forage and rate of intake to determine suitability for good doers. As little or no fermentation occurs with wrapped hay, the WSC levels are typically like hay.
Of the forages tested for starch the maximum value we saw was 2.3% which is typical of the 2-3% averages. It is interesting to note that if we calculate the NSC values for these forages (the sum of WSC and starch) only 14.3% of the samples tested last year would meet the target of 10-12% NSC which is advocated for laminitis-prone individuals.
Putting this in to practice
If you have a good do-er and your forage falls into the 85.7% of less desirable NSC results or it is not practical to test your forage as you don’t have a consistent supply, what steps can you take?
Other than switching to an alternative forage source, soaking is one option to reduce the NSC content of your forage. There are disadvantages to soaking hay, not least from the amount of water used and its effect on the environment, but it also results in a very heavy net for us to lift and is more difficult to put into practice in the winter during freezing conditions. Another more sustainable option is to consider mixing straw through the forage ration to lower the overall NSC intake whilst also significantly reducing the DE intake as well. We discuss all of these issues and more in our Weight Management and Laminitis Guide.
A final thought
Forage analysis is only one part of the picture. Whilst 10-12% NSC is given as a guide, it is just that. Some laminitis prone individuals may be managed well on forages that are potentially higher NSC than this whilst for others this may still be too high – there is a lot of individual variability in relation to metabolic issues. If you are the owner of a laminitis-prone individual, our advice would be to work with your vet to monitor your horse’s insulinaemic response to feed. These results will help to demonstrate your horse’s risk of laminitis and inform their dietary management too.
For more information on what to feed your horse or pony or for help and advice on all aspects of feeding call the Dengie Feedline: 01621 841188 or complete our Feed Advice Form.
