Purple pigeon grass (Setaria incrassata): a potential cause of nutritional secondary hyperpharathyroidism of grazing horses.

The research article discusses the potential risk posed by the Purple pigeon grass (Setaria incrassata) in causing Nutritional Secondary Hyperparathyroidism (NSH) in horses.

Introduction to Purple Pigeon Grass

• This grass is a perennial plant native to Zimbabwe and Transvaal in southern Africa, known for its drought tolerant characteristics, making it suitable as fodder for cattle and sheep.
• Its usage has expanded to Queensland due to the decline of native Mitchell grass and as an alternative to white spear grass, which contaminates wool.
• It’s also used in regions where financial returns from grain production are low and farmers are shifting towards beef production.

Nutritional Secondary Hyperparathyroidism (NSH)

• NSH is a disease affecting horses that graze on tropical pasture grasses, causing them serious health problems. The condition arises when horses are unable to derive enough calcium (Ca) from their feed to support physiological needs.
• NSH has been observed in horses grazing exclusively on Setaria species due to the prevalence of calcium oxalate crystals in the grass, from which horses can’t extract sufficient calcium.
• The researchers found similarities between S. incrassata, the Purple pigeon grass, and S. sphacelata, a grass species known to cause NSH in horses, leading to this investigation.

Research Methodology and Findings

• The researchers collected and analyzed dried samples of S. incrassata leaf and stem for calcium, phosphorus and total oxalates.
• It was determined that grasses with calcium to total oxalate ratios of less than 0.5 were capable of causing NSH in horses and S. incrassata met this criterion.
• The researchers concluded that S. incrassata should not be used as a pasture for horses for extended periods unless an adequate alternative supply of calcium and phosphorus is available.
• Though there were no reported cases of NSH in association with S. incrassata, the researchers warned of its potential to cause the condition in horses.

Conclusions and Future Directions

• This research was conducted to alert veterinarians and pasture management advisers to this potential risk.
• The identification of S. incrassata as a potential cause of NSH in horses will contribute to preventing such occurrences by informing suitable pasture management practices.