Influence of Endophyte-Infected Tall Fescue Seed Consumption on the Establishment and Maintenance of Pregnancy in Mares

Abstract

<h2>ABSTRACT</h2> Twelve nonlactating mares of light horse breeding were used to determine the influence of fescue seed consumption on the establishment and maintenance of early pregnancy. Mares were allotted randomly to receive fescue seed-based diets with no ergovaline (NE) or containing 158 (low ergovaline: LE) or 315 (high ergovaline: HE) ppb ergovaline/kg of total diet fed. Mares consumed diets for a minimum of 7 d before breeding was initiated. During estrus, mares were sonographically monitored daily for ovarian activity. Mares were monitored weekly for rectal temperature (TEMP), body condition (BCS), and weight (BW). Serum samples were harvested weekly to measure circulating concentrations of progesterone (P₄) and prolactin (PRL). Following establishment of pregnancy, embryonic vesicular size was estimated sonographically on d 14, 21, and 28. The consumption of diets without ergovaline or 150 or 308ppb ergovaline had no influence on TEMP or BCS. However, mares consuming 308ppb ergovaline/kg total diet tended to lose weight as compared to mares consuming diets lacking ergovaline. Circulating concentrations of P₄ during the luteal phase were lower for mares consuming diets without ergovaline than for mares receiving diets containing ergovaline. Serum PRL concentrations were suppressed in mares that consumed diets containing ergovaline. Overall conception rates, cycles per conception, and embryonic vesicular sizes did not differ between mares consuming diets containing increasing concentrations of ergovaline. These data suggest that diets containing up to 308ppb ergovaline/kg total diet have no adverse effects on the establishment and maintenance of pregnancy through d 28.