Green Feed Rickets

​​About Green Feed Rickets​

Green feed rickets is a term used to describe a syndrome that can occur in lambs due to an imbalance in calcium, phosphorous and Vitamin D ratios. 

It is more commonly seen in unshorn lambs and weaners that are deficient in Vitamin D, which is highly important in regulating the body’s calcium and phosphorous levels. Rapidly growing ram lambs are most at risk. Weather conditions and time of year influence Vitamin D levels, and there have been correlations to rickets with winter feeding on lush ryegrass pasture or cereal crops such as oats. 

Vitamin D is produced by the skin when exposed to UVB radiation in sunlight. Vitamin D has many roles in the body, including controlling phosphorus and calcium absorption from the intestine, and to and from the bones. Ewes can supply sufficient Vitamin D in their milk for the first 4-6 weeks of a lamb's life, after which time a lamb must obtain its own Vitamin D. 

Vitamin D is available in various oils (particularly fish oils) and fresh, sun-cured hay (Vitamin D levels in sun-cured hay will decrease with prolonged storage). Vitamin D is stored in the animal's fat, so an adult animal is less susceptible to seasonal variations in Vitamin D levels compared to younger classes, due to their higher fat reserves.​

In Tasmania and parts of southern Victoria there is often insufficient UVB radiation in the sunlight for Vitamin D production, particularly over winter months. Sheep with black pigmented skin, or long wool, and self-shedding sheep require more UVB radiation to produce Vitamin D than white skinned and short wooled sheep.  

Sheep grazing cereal crops with high carotene or Vitamin A levels (such as oats), will require higher levels of Vitamin D, and as such, there is an increased risk of green feed rickets in lambs consuming greenfeed in winter, when UVB radiation is lowest.


Signs of green feed rickets can include abnormally high incidence of broken bones, Ill-thrift in lambs and weaners combined with stiffness or shifting lameness, hunched back, reluctance to stand, milk fever in lactating ewes, and skeletal deformities such as enlarged joints, bowlegs, knock knees, or lumps along the rib cage where the rib bones join the rib cartilage. Loose teeth and tooth rot may also be due to rickets.

​Blood tests may be misleading and definitive diagnosis is often achieved by analysing the bone ash of a foot bone post mortem.


Provision of good quality sun-cured hay is the simplest prevention, particularly for animals at risk.
Injectable and oral Vitamin D supplements are also available. 

Consult your veterinarian regarding the best options for diagnosis, management, prevention and treatment if you suspect green feed rickets in your flock.


Animal Disease Enquiries

13 St Johns Avenue,
New Town, TAS, 7008.