What is Bighead?
Being in central Queensland, unless horses are kept stabled with 100% hay or supplement feeding, there is a very high likelihood of exposure to buffel grass. Buffel grass contains a compound called oxalates which when ingested bind calcium and make in unavailable to the body. The body’s response to these low levels of calcium is to release a hormone called parathyroid hormone (PTH) which aims to draw more calcium from the kidneys, intestines and most importantly the bones. If this continues for long periods of time it can cause osteoporosis and fibrosis. This is called Equine Nutritional Secondary Hyperparathyroidism which is also known as Bighead.
What are the clinical signs of Bighead?
Commonly we see:
-
- Ill thrift
- Swelling around the nasal bones or jaw
Less commonly we can also see:
- Loss of appetite
- Pain chewing
- Swelling of the pastern
- Clear nasal discharge
- Pain in their back
How do we diagnose Bighead?
Often clients will expect bloods to be taken to diagnose bighead in their horses. Unfortunately the Calcium and Phosphorus levels of the blood are often normal, because the body is compensating bu releasing PTH and normalising Calcium levels in the blood. It is the removal of calcium in the bone that is the problem therefore diagnosis can be tricky. We will often use a diet assessment of their current diet, clinical signs and physical exam to make a presumptive diagnosis.
Radiographs can be taken of the fetlocks/pastern joint or the face to assess for signs of osteoporosis however changes in calcification of the bone will only happen in very late stages of the disease.
How to treat and prevent Bighead?
Dietary supplementation is the only way to combat Bighead. There are MANY products on the market which claim to be high in calcium and targeted for bighead prevention, however unfortunately there are no regulatory bodies in place to guarantee quality of these products, meaning many are useless.
Treating bighead requires not only increasing the dietary calcium, but ensuring the calcium:phosphorus ratios in the diet are over 2:1 otherwise there will be no resolution of disease. As well as this, calcium need to be “chelated” meaning it will be ingested and absorbed rather than ingested and bound by oxalates and pooed out. Magnesium and salt is often required to improve calcium absorption in the gut as well.
Unfortunately many products don’t have chelated calcium, don’t have the appropriate calcium phosphorus ratios or don’t have enough calcium at all. The best products available are:
- Calsorb lick blocks
- Bone Formula powder (must be fed daily not weekly)
Our recommendation for horses suffering from bighead, or in high risk paddocks (almost all paddocks in CQ) is to have hay available to reduce the quantity of buffel ingested and have a Calsorb lick block available at all times (ensure enough lick blocks if you have multiple horses). If you are feeding your horses daily you can include Bone Formula into the feed instead of a lick block. Any additional products added on top of these may alter the Ca:Ph and worsen the condition. Keeping it simple is often best, and feeding a good quality well researched product in the right quantity at the right frequency will be all that is needed.
Keep in mind if your horse is showing severe signs of bighead they may need veterinary intervention.
If you have any further questions regarding Bighead please feel free to contact us on 4985 2552 to chat to the team.