Osteodystrophia fibrosa in horses at pasture in Queensland: field and laboratory observations.

The study observes that horses grazing on specific types of grasses in Queensland developed symptoms of a bone disease called osteodystrophia fibrosa. The grasses were found to contain oxalates that may be the cause of the disease even though other mineral levels in the pasture were normal.

Context and Purpose of the Research

• The research was conducted in response to cases where horses grazing on certain pastures in central and coastal Queensland developed a bone disease known as osteodystrophia fibrosa.
• The purpose of the study was to ascertain why this was happening, whether it was due to the type of grass that the horses were grazing on and whether the pastures or grasses contained any harmful elements causing the disease.

Findings of the Study

• The study found that horses grazing mainly on Cenchrus ciliaris and/or Panicum maximum var. trichoglume pastures in over 30 properties in southern central Queensland developed lesions of osteodystrophia fibrosa, a disease that causes weakening and deformation of bones.
• Similar cases were noted in horses grazing on Setaria anceps, Brachiaria mutica or Pennisetum clandestinum pastures in coastal Queensland.
• The indications of osteodystrophia fibrosa observed in the horses included ill-thrift, lameness, and fibrous swellings of nasal bones, maxillae and mandibles.

Key Implications and Conclusions

• An analysis of the grass types and the pasture composition showed that calcium and phosphorus levels were normal and did not contribute to the disease. However, all the grass types that the horses were feeding on contained oxalates. Thus, the researchers suspect that the oxalates were causing the disease.
• The pasture species that caused osteodystrophia fibrosa have not been previously known to contain enough oxalates to cause ill effects. This indicates that further research would be required to validate the hypothesis.
• The findings imply that the management of such pastures might need to consider the possible detrimental effects of oxalates on horse health.