June2011_BIG HEAD
– big problem?
What is big head? Big head, or nutritional secondary hyperparathyroidism, occurs when the body can’t absorb enough calcium to meet daily requirements, whether through deficiency or problems with absorption.
Calcium has many roles in the body – it makes up approximately 35% of the skeletal structure and assists in controlling muscle contractions and many metabolic, gastrointestinal and nerve functions. The body tightly regulates the calcium levels in the blood. When the diet contains an incorrect balance of calcium and phosphorous the parathyroid gland releases a hormone to increase the calcium levels in the blood- it does this by dissolving the bones. This leads to the signs we see as ‘big head’ when fibrous tissue replaces the bone. There is often a shifting lameness, weight loss and facial swelling under the eyes and on the jaw. This is because the body takes calcium from the non-weight bearing bones, such as the head first. As the disease progresses, fractures are also common.
Why does it occur? Tropical grasses (Setaria, Buffel, Kikuyu) contain oxalates. These bind calcium and prevent its absorption through the gut, therefore reducing the levels in the blood and activating the parathyroid gland. If this is the main or sole grass type in a paddock then onset of disease can occur in as little as 2 months with clinical signs obvious to owners normally around 6 months. These worsen with continued exposure.
Prevention- keeping horses on pastures containing little to no tropical grasses is the ideal, however in reality is hard to achieve. Lucerne is a great source of calcium and should be fed as an extra to grazing. It will reduce grass intake and increase the amount of calcium absorbed. There are also mineral supplements that need feeding in a specific ratio to restore the correct calcium balance as well as commercial pre mixed feeds. For advice on the correct supplementation for prevention or correction or if you are worried about big head in your horse contact the Old Mill Vets who can advise you on the best treatment/prevention plan.
Why does it occur? Tropical grasses (Setaria, Buffel, Kikuyu) contain oxalates. These bind calcium and prevent its absorption through the gut, therefore reducing the levels in the blood and activating the parathyroid gland. If this is the main or sole grass type in a paddock then onset of disease can occur in as little as 2 months with clinical signs obvious to owners normally around 6 months. These worsen with continued exposure.
Prevention- keeping horses on pastures containing little to no tropical grasses is the ideal, however in reality is hard to achieve. Lucerne is a great source of calcium and should be fed as an extra to grazing. It will reduce grass intake and increase the amount of calcium absorbed. There are also mineral supplements that need feeding in a specific ratio to restore the correct calcium balance as well as commercial pre mixed feeds. For advice on the correct supplementation for prevention or correction or if you are worried about big head in your horse contact the Old Mill Vets who can advise you on the best treatment/prevention plan.
