Case-control study of factors associated with excessive proportions of early fetal losses associated with mare reproductive loss syndrome in central Kentucky during 2001.

This study investigates what factors are associated with an excessive number of early fetal losses in mares, specifically within the context of mare reproductive loss syndrome, in Central Kentucky during 2001. The research found that exposure to moderate to high concentrations of Eastern tent caterpillars, cherry trees, farm size of 50 or more broodmares, being bred in February 2001, and frequent exposure to waterfowl increased the risk of these early fetal losses. Lower risks were associated with feeding hay to mares outdoors.

Study Methodology

• The researchers conducted a case-control study, using questionnaires to gather data about
  possible factors linked with mare reproductive loss syndrome. These potential factors were
  categorized as farm-, pasture-, and individual animal-level factors.
• Information was gathered from 133 farms, with 97 recording excessive early fetal loss rates
  and 36 serving as control farms. These 133 farms represented a total of 6,576 mares.
• On six farms, representing 340 mares, individual animal-level factors, such as age, parity,
  and pre- and postbreeding treatments, were also examined.

Results of the Study

• Increased risk of excessive early fetal losses were notably associated with the following
  factors:
  • Mares exposed to moderate to high concentrations of Eastern tent caterpillars.
  • Mares exposed to cherry trees.
  • Farm size of 50 or more broodmares.
  • Mares bred during February of 2001.
  • Frequent exposure to waterfowl.
• The study discovered that feeding hay to mares outside was associated with a decreased risk
  of excessive early fetal losses.
• Pasture composition and management factors did not significantly differ between affected
  and control pastures.
• Individual animal-level factors, such as age, parity, and pre- and postbreeding treatments,
  were not found to be significantly associated with the risk of early fetal loss.

Conclusion of the Study

• This research suggests that certain measures can be taken to reduce the risk of
  excessive proportions of early fetal losses linked to mare reproductive loss syndrome. These
  measures include limiting mare exposure to Eastern tent caterpillars and cherry trees, as
  well as feeding hay to mares outdoors.