Prolonged gestation, decreased triiodothyronine concentration, and thyroid gland histomorphologic features in newborn foals of mares grazing Acremonion coenophialum-infected fescue.

The research examines the impact of Acremonium coenophialum-infected fescue on the gestation duration and thyroid activity in newborn foals when grazed by mares at different stages of their pregnancy.

Summary of Study and Findings

• The study was designed to understand the prolonged gestation durations and thyroid gland abnormalities in newborn foals when their mare mothers grazed on Acremonium coenophialum-infected fescue. This fungus, commonly found in fescue grass, was tested to see the effects on pregnant mares and their subsequent foal offspring.
• Four experimental groups were set up: mares grazing on endophyte-free fescue (E-); mares grazing continuously on endophyte-infected fescue (E+); mares grazing on E+ fescue from gestation day 300 until birth; and mares grazing on E+ fescue from conception to gestation day 300.
• Foals born to mares exposed to the endophyte late in gestation demonstrated larger, inflated thyroid follicles lined with flat cuboidal epithelial cells, implying a possible alteration of the thyroid structure due to the infected fescue.
• Measurements also revealed a significant decrease in triiodothyronine concentration—an important thyroid hormone—in foals exposed to the endophyte (395.2 ng/dl) compared to the control group of foals (778.0 ng/dl).
• Thyroxine and reverse triiodothyronine concentrations, also important for thyroid function, were not significantly different among the groups, indicating the fungus specifically influences triiodothyronine levels.
• The researchers found no significant differences in organ weight as a percentage of body weight among the different groups of foals, suggesting the impact of the fungus is primarily seen in the gestation duration and thyroid activity of the newborn foals.

Conclusion

• The study concludes that grazing on Acremonium coenophialum-infected fescue influences the gestation period and thyroid gland function in newborn foals of mares exposed to the infected grass late in gestation.
• This provides valuable insights into the potential risks associated with feeding pregnant mares with infected fescue, emphasizing the importance of careful feed selection for pregnant livestock to prevent possible health ramifications in their offspring.