Polyneuropathy associated with forage sources in Norwegian horses.

This research article investigates the occurrence of hindlimb weakness in Norwegian horses, linking it to their diets and environmental factors. The researchers propose that the weakness is caused by polyneuropathy, a nerve disorder that affects multiple nerves.

Research Hypothesis

• The researchers hypothesized that the hindlimb digital extensor weakness observed in the horses arose from polyneuropathy of the distal nerves. They further proposed that this condition could be linked to environmental factors, notably the horses’ diet.

Methods and Sample Population

• The study involved a total of 75 horses exhibiting symptoms of digital extensor weakness. The cases, recorded between 1995 and 2004, included horses of different ages, genders, and breeds, implying a wide-ranging issue.
• Most of the involved horses were used for leisure or breeding purposes. The records of horse examination conducted at The Norwegian School of Veterinary Science and ambulatory practices were used for reference.

Results and Observations

• The diagnosed horses showed varying symptoms, ranging from intermittent hindlimb knuckling to severe paraplegia. Some presented no progression or only slow progression of the symptoms, while others quickly developed severe indications.
• No other neurological deficits were identified in these horses, and there was no substantial evidence suggesting an infectious cause. Indeed, the significant common factor between the affected horses was that they all consumed large bale silage or poor microbiological quality hay. Forty horses among the sample population were euthanized due to their condition.
• Histopathological examination of the peripheral nervous tissues conducted on 22 horses revealed neuronal fiber degeneration. The majority of the horses exhibiting mild symptoms recovered after around 5-6 months of rest.

Conclusions

• The study concluded that the observed clinical signs could be correlated with polyneuropathy affecting the sciatic nerves. Furthermore, the findings imply a possible link between the horses’ forage sources and the occurrence of this neurological disorder.