Equilibrium Australia - It's all in the Balance
  • Home
  • About
  • Rider Advocates
  • Testimonials
  • Products
    • Australia
      • Equilibrium B1 Cool Mix
        • B1 Cool Mix 5kg
        • B1 Cool Mix 12kg
        • B1 Cool Mix 22kg
      • Equilibrium Mineral Mix
        • Mineral Mix 5kg
        • Mineral Mix 12kg
        • Mineral Mix 22kg
    • New Zealand
      • Equilibrium B1 Cool Mix
        • B1 Cool Mix 5kg
        • B1 Cool Mix 12kg
        • B1 Cool Mix 22kg
      • Equilibrium Mineral Mix
        • Mineral Mix 5kg
        • Mineral Mix 12kg
        • Mineral Mix 22kg
  • Information
    • Fact Sheets
    • 2MR – What Could My Feed Be Telling Me?
  • Find a Stockist
  • Contact
  • Search
  • Menu
  • 0Shopping Cart

Secondary Nutritional Hyperparathyroidism

The information contained within each of these PDFs is intended to be general in nature and assist horse owners by providing them with a little more background on various subjects. This information should NEVER be considered to be a replacement for advice received by your equine vet or nutritionist.

Hyperparathyroidism

Big Head, as it is commonly referred to, is a complex nutritional problem that has its origins in a calcium – phosphorus imbalance in the diet. This is different to an absolute lack of calcium in the diet which results in different clinical signs.

Calcium and phosphorus are macro-minerals that are needed by the body in absolute amounts to perform the jobs required by the body. In addition they are required to be present in the correct ratio to each other in the diet.

Calcium and phosphorus are present in bone in a ratio of approximately 2:1 and bone is a reservoir of these minerals for a period of time if the diet is deficient. Blood levels of calcium are rigidly maintained at between 2.9-3.9 mmol/litre; phosphorus has a far wider range of measured values in the blood with no adverse effects.

What causes Bran Disease?

When bran was traditionally a large part of the horse’s diet, it was observed that many horses developed a “big head” which progressed over time to poor work performance and ultimately to fractured bones and euthanasia. The reason for it was unknown. It is only comparatively recently that the role bran plays in the development of big head has become understood.

Bran has ten times more phosphorus than calcium which immediately upsets the required ratio; in addition the phytic acid in bran binds both calcium and phosphorus and decreases absorption from the gut. Copper, zinc and manganese absorption are also affected by phytic acid so that big head becomes a multifactorial mineral imbalance. Grain also has high phosphorus and low calcium levels and contains phytic acid.

Why do oxalate-containing plants cause Big Head?

Some pasture plants contain oxalic acid which binds the calcium in the plant to form calcium oxalate which is stored in the leaf and stem. This insoluble form of calcium oxalate means that very little calcium is available in the plant for the horse to utilise. Some oxalate plants contain a large amount of calcium and if the calcium to oxalate ratio is 0.5:1 then it is relatively safe to graze. A flush of growth after rain tends to increase the oxalate levels – anecdotal evidence is that there is a higher incidence of Big Head after rain.

Some pasture plants contain a soluble form of calcium oxalate which can lead to acute oxalate poisoning. There is rapid binding of serum calcium to the oxalate which leads to a precipitous drop in blood calcium. Affected animals develop muscle tremors, staggers, depression and ultimately death due to heart failure. These plants have more than 2% dry matter oxalic acid and are generally very unpalatable. Horses have to be starving to eat them – it is a sign of very bad horse husbandry to have this situation develop.

What are the clinical signs of Big Head?

It takes approximately two months on high oxalate pastures for signs to develop – generally it is six to eight months for most horses on moderate oxalic pastures. The chronically low blood calcium levels due to inadequate intake of calcium causes the parathyroid gland to release parathyroid hormone. This hormone stimulates the release of calcium from the bones to increase the levels in the blood stream. The calcium is mainly sourced from the long bones of the legs and the bones of the head. Over time as the bones become demineralised there is lameness, weight loss, swelling of the lower jaw bone, stiffness and short stepping. As the condition progresses both jaw bones and facial bones increase in size due to the laying down of fibrous tissue in place of bone. Arthritis

develops and the parathyroid glands become enlarged – hence the correct name for this condition is secondary nutritional hyperparathyroidism. Left untreated, the bones fracture and horses need to be euthanasiaed.

What is the treatment for this condition?

Veterinary examination is needed to confirm that this is indeed the problem and then attention is directed to correct the dietary deficiencies and imbalances. Adding calcium alone is often inadequate especially in long standing chronic cases. A balanced multi-mineral and vitamin supplement is required to address the overall nutritional status of affected horses.

Some swellings of the head may never totally resolve and it takes up to twelve months for bones to remineralise. Horses must not be worked in this time and they must be given absolute paddock rest to recuperate. It is important that they have some free ranging movement as the bone remineralises in order to strengthen and remodel the bones back to normal anatomy and physiology.

What pasture plants contain oxalates?

Native pasture plants do not contain oxalates – the problem plants are subtropical pasture plants introduced for grazing cattle on. Cattle are more resistant to oxalic acid activity due to their rumen digestion in the foregut.

If horses are on these pastures make grassy hay a major part of their diet – do not fertilise with poultry manure or superphosphate – place the horses on a well-balanced multi-mineral vitamin supplement – and where possible reseed pastures to non oxalic acid containing plants.

The following is the average calcium to oxalic acid ratio in different pasture plants:

  • Kikuyu 0.23:1 – there is rapid summer growth and it becomes rank and unpalatable fairly quickly – widespread pasture plant
  • Buffel 0.22:1
  • Pangola 0.37:1
  • Green Panic 0.32:1
  • Para Grass 0.29:1
  • Pig Weed 4.5 -9.4% dry matter –causes the acute oxalate poisoning.
  • Setaria 0.15:1

Setaria has four main cultivars – Nandi, Naok, Solander and Kazungula. The latter has the highest level of oxalic acid and can be up to 7% DM. It grows only in high rainfall areas and needs more than 1100mm rain annually. It is extremely toxic to horses and lactating cows. It is highly recommended that horses do not graze this cultivar at all as no amount of mineral supplementation appears to be able to stop Big Head developing.

Oxalates in general are more concentrated in the leaves than in the stems of plants, the levels are higher in younger plants, and phosphorus and nitrogen fertiliser stimulate higher oxalate levels.

Don’t graze horses on fertilised pastures, don’t graze at night when oxalate levels are elevated and do not graze equines for more than one month in any summer on Kazungula Setaria pastures.

Australia

Phone: 1300 720 377

Phone (International):
+61 7 3200 4844

Fax: +61 7 3200 4847

Mail:  PO Box 4605
Loganholme DC
QLD 4129 Australia

New Zealand

Horse Owner Enquiries
(Product and Nutrition Advice): 0800 442 450

Placing Orders for
Equilibrium Product: 09 829 0456

Fax: 09 828 1599

Mail: Private Bag 47908
Ponsonby
Auckland

United Kingdom

Phone: 01488 73322

Boomerang Nutrition Ltd
Stance Equitec UK Pty Ltd

Mail: Unit A4, Groundwell Industrial Estate,
Stephenson Road
Swindon
SN25 5AX

www.boomerangnutrition.co.uk 

© Copyright - Equilibrium Australia - It's all in the Balance - Enfold WordPress Theme by Kriesi
Scroll to top

This site uses cookies. By continuing to browse the site, you are agreeing to our use of cookies.

OKLearn more

Cookie and Privacy Settings

How we use cookies

We may request cookies to be set on your device. We use cookies to let us know when you visit our websites, how you interact with us, to enrich your user experience, and to customize your relationship with our website.

Click on the different category headings to find out more. You can also change some of your preferences. Note that blocking some types of cookies may impact your experience on our websites and the services we are able to offer.

Essential Website Cookies

These cookies are strictly necessary to provide you with services available through our website and to use some of its features.

Because these cookies are strictly necessary to deliver the website, you cannot refuse them without impacting how our site functions. You can block or delete them by changing your browser settings and force blocking all cookies on this website.

Google Analytics Cookies

These cookies collect information that is used either in aggregate form to help us understand how our website is being used or how effective our marketing campaigns are, or to help us customize our website and application for you in order to enhance your experience.

If you do not want that we track your visist to our site you can disable tracking in your browser here:

Other external services

We also use different external services like Google Webfonts, Google Maps and external Video providers. Since these providers may collect personal data like your IP address we allow you to block them here. Please be aware that this might heavily reduce the functionality and appearance of our site. Changes will take effect once you reload the page.

Google Webfont Settings:

Google Map Settings:

Vimeo and Youtube video embeds:

Privacy Policy

You can read about our cookies and privacy settings in detail on our Privacy Policy Page.