A relatively mild winter combined with an exceptionally mild January means that our grass has not stopped growing and right now has a head-start on luscious Spring growth.  Especially for horses who are on livery yard with a winter schedule (out grazing for daylight hours, brought in at night), the time out on newly lush grass may be causing issues.  So what are these issues and why do they happen?

Horses digest fibre (ie grass) by fermenting it in the large intestine, an area known as the hindgut.  Fermentation mostly occurs in the caecum, a huge tube of about 30 litres capacity, which is full of many species of bacteria.  These bacteria, or microflora, work together to digest the fibre through the fermentation process, and in turn, produce absorbable products of digestion.  When the fibre is high in sugars, such as in lush Spring grass, more acid is produced by this digestion process, which lowers the pH of the caecum.  Bacteria are very particular about the pH they can survive in, and by lowering the pH the balance between different species is upset.  When there is a change to the balance of bacteria we can get over-production of gas, or other by-products of digestion, which lead to bloating, constipation, constipation or diarrhoea.  This can cause local tissue inflammation and neuropathic irritation.

Neuropathic irritation is when a problem, such as bloating or inflammation, causes increased firing of the nerve endings attached to the caecum.  These irritated nerve signals travel to their specific spinal cord segment (in this case the lumbar segment), and as a result there is increased tension and often pain in the musculature surrounding that spinal segment.  Nerve signals travel both ways, so an injured or stiff spinal segment can compound the problem.  Back pain or tension often correlates with organ issues – it is why people with IBS are more likely to have back pain, and people with back pain often develop IBS.  This relationship can continue to spiral and include other organs within the same spinal segment – most notably ovaries in mares.

In addition to neuropathic irritation, we have a local acidosis (decrease in blood pH caused by excessive acid production by the microflora).  Acidosis causes contraction (shortening) of fascia.  Fascia is bands/sheets of connective tissue that attach to, stabilise, enclose, and separates muscles and other internal organs.  As you can imagine, contraction of fascia results in reduced mobility and a “tight” feeling.  This usually starts locally, ie in the right hind quadrant where the caecum is.  You may notice muscle tension, unsoundness or lameness in the right hind leg initially.    If left untreated, the acidosis and following fascial contraction can spread throughout the body. 

Neuropathic irritation and acidosis may present as:

• Flank sensitivity
• “Girthiness”
• Tension in muscles surrounding the lower (lumbar) spine
• Saddle slipping to the left
• Not tracking up
• Toe scuffing or dragging (right hind)
• Lameness (right hind)
• Canter issues – transitions, left canter
• Leg lifting – unhappy to lift the leg, kicking out
• Not moving forward off the leg
• Bucking
• Extreme behaviours coinciding with being in season
• Poll tension or headshaking

So what can you do about it? As always, if you have any suspicion of a problem with your horse it is important to look at the whole picture. Don’t focus solely on the one lame leg – you could miss the root cause of the issue. By the same token, a holistic treatment plan tackles the problem from multiple angles:

Environment: consider changing your routine from the normal winter schedule. Having them out at night when the sugars are lower may be a better idea than when the sun is shining. Consider restricted grazing areas, or supply hay (which is lower in sugars) as a buffer.

Exercise: maintain mobility by ensuring your horse gets regular exercise either ridden or in hand, and that they move their body correctly and evenly.

Bodywork: consider physiotherapy, massage, acupuncture or laser treatment for tight muscles.

Medication/supplements: herbal medicines that buffer the hindgut, stimulate digestion, are prebiotic (feeding the microflora), and antispasmodic can help lessen the impact of lush grass and smooth the transition into Spring.

Remember, doing any one of these things alone is unlikely to be effective. By tackling the body-wide tension and protecting gut health you can ensure your horse enjoys a comfortable and happy transition of seasons.