Summer finally seems to have graced us with its presence after some extremely changeable weather at the end of spring. Rain one minute and then sunshine the next can be a nightmare for rugging horses and staying dry in the saddle, but it did mean that the grass in UK fields grew well and many people now have a good growth of grass to manage over the coming months. Good grazing represents the most cost-effective and environmentally-friendly feedstuff available to horse owners, but most of us have limited turnout and/or horses with specific dietary requirements to manage. This means we need to look at our grassland management in more detail to ensure we look after our fields.

How does grass grow? 

As we move through summer the weather and the number of horses grazing on it will influence grass growth, and it helps to understand how and why grass grows in the first place.

1. Firstly, grass needs three things – light, warmth and nutrients (including water) – to grow. The leaves, the softest and least fibrous part of grass, turn light into soluble carbohydrates via the process of photosynthesis.
2. These soluble carbohydrates are simple sugars which fuel the growth of the plant.
3. Photosynthesis stops when the sun goes down each evening, but growth will continue throughout the night, provided it is damp enough and the temperature doesn’t fall too low.
4. During the growth process soluble carbohydrates are converted into structural carbohydrates, growing larger, soft leaves first, then roots and stems which are more fibrous.
5. Grass is at its most nutritious (in terms of energy, protein, fibre, vitamins and minerals) when it is growing the stem. This is because once it reaches the optimum height it will bud, forming a flower and at this stage protein levels suddenly drop.
6. If the grass remains uncut for silage then the flower will be fertilised, and the sugars produced during photosynthesis will form starch in seeds or grains as they develop.
7. Once the seeds or grains are fully developed the grass will shed them, leaving the parent plant low on protein and starch, and starting the process of it dying back. Photosynthesised sugars are stored in the base of the plant as opposed to the leaves, ready for it to grow again the following spring.

How does a horse know when it is full? 

To take this knowledge of the nutritional content of grasses at different stages of growth and use it to work out how to manage our grassland, we must then examine what makes a horse feel ‘full’. The equine appetite is satisfied by the volume of fibrous dry matter that they consume (so the bulk) rather than the calories their food contains.

This means that a horse turned out on over-grazed grass with a short sward (shorter than 2cm) will only be able to graze on the leaves as there is no chance for stems and roots to develop properly. Even if they eat all day long, they will still feel hungry because they are eating only low fibre forage – and there’s a risk they could damage their teeth on soil particles too.

Overgrazing or over-growth? 

Grazing right down to soil level will also impact the grass that grows, stunting or killing off desirable native grasses and allowing ryegrass, docks and weeds to thrive. It also means your fields are more susceptible to drought and waterlogging. So, what about keeping grass lush and long instead? We can take a look at how farmers who are raising livestock for milk or meat operate. They carefully manage their grassland with topping and grazing to keep it constantly in the ‘growth’ phase where the nutritional content is highest. This means their livestock will gain weight quickly.

Grazing equines on grass managed in a similar way will have the same effect – they will likely gain weight rapidly. This is because they are still mainly eating rich, soft and highly calorific leaves as the plant is yet to energy into seed and grain production. They may eat all day long without getting the fibre intake they need to feel full and if they are prone to laminitis, you could be in trouble.

Getting the balance just right

So, what is the answer to getting summer grazing right? It could be easy to read this and think that there is no right way, but it is worth bearing several things in mind. Firstly, horses have evolved to lose weight naturally in the winter, but we tend to prevent this through overfeeding and over-rugging them during the colder months. This means that instead of the extra nutrition in grass in the summer simply bringing them back to healthy condition and preparing their body for the harsh winter ahead, it makes them fat. Not allowing your horse to stay too round in the winter months will help – their weight should fluctuate naturally throughout the seasons.

Secondly, you may need to adjust your routine depending on the condition of each individual horse. Bringing a horse in before lunchtime means they will avoid eating grass with the highest sugar load. Rather than restrict overweight horses to a tiny area of grazing where they don’t have space to move far, why not turn them out on a larger, artificially surfaced area where they can stretch their legs – with access to steamed hay for forage, of course. Use your grass turnout that is unused to then grow stemmy hay which, when dried, will provide a wonderful source of fibre-rich forage.

Going the extra mile for UK biodiversity

It’s also worth mentioning that by leaving unfertilised ‘set aside’ margins of 5-10cm around all grazing areas you will encourage herbs and grasses to grow which will then seed your grazed areas for you. For example, organic farmers sow chicory in margins which, while it won’t stand up to over grazing, will add minerals such as copper and zinc into the soil (and these are two of the very minerals UK soil is often lacking!). There are also ongoing experiments with keeping horses in woodland grazing habitats, which offer natural shelter, a range of fibrous forage and predator species to manage flies – watch this space!