Chronic selenosis in horses fed locally produced alfalfa hay.

The research paper discusses cases of chronic selenosis (alkali disease) in horses in western Iowa where horses were fed locally produced alfalfa hay, identified as the primary source of the condition. The study further demonstrates the challenges faced during diagnosis due to diversified tissue concentration, inconsistent sample selenium concentrations and varying recommendations on sample selection and diagnostic value.

Chronic Selenosis and its Association with Alfalfa Hay

In the research, chronic selenosis, also known as alkali disease, was discovered in horses in western Iowa, a region associated with marginally to adequately soil selenium. Here, soil selenium refers to the amount of selenium present in the soil where the alfalfa is grown. Selenium in high concentrations can be toxic and can lead to selenosis. The primary source of this condition was traced back to two locally produced alfalfa hays.

• The alfalfa hay was found to contain high levels of selenium that led to the unfortunate health condition in the horses.
• Chronic selenosis presents a challenge in horses drawing from its similarity with other diseases and the absence of a timeline for the disease’s development.

Challenges in Diagnosis

The study notes that selecting diagnostic specimens to evaluate potential chronic selenosis cases is problematic due to a variety of issues:

• The wide range of tissue concentrations observed in different cases. This means that selenium accumulates in tissues to varying degrees, making it difficult to establish a benchmark for diagnosis.
• Conflicting correlations of selenium concentrations in different studies. Different studies report different selenium concentrations in samples, causing confusion and making diagnosis difficult.
• Differing recommendations on specimen selection and diagnostic value. Due to the inconsistent findings, there is no universally agreed-upon method for specimen selection or means to diagnose the disease.

Recommendations

The paper concludes with recommendations aimed at enhancing the diagnosis of chronic selenosis. It stresses the need for multiple sample collections which will be instrumental in confirming high selenium concentration in various tissues and identifying selenium sources.

• However, the study also highlights that samples believed to reflect historical exposure versus current status may be questionable.
• The research advises that practitioners interpreting the results should take into consideration the selenium exposure level and duration, antagonistic or ameliorating factors, and post-exposure excretion.