Effects of short-term early gestational exposure to endophyte-infected tall fescue diets on plasma 3,4-dihydroxyphenyl acetic acid and fetal development in mares1,2

Abstract

Consumption of wild-type (toxic) endophyte-infected tall fescue (E+) by horses during late gestation is known to adversely affect pregnancy outcome; however, little is known of the potential disruptive consequences of E+ consumption by mares during the critical phases of placentation and fetal development in early pregnancy. The objective of this study was to evaluate the detrimental effects of feeding E+ to mares during early gestation. Mares (n = 12) paired by stage of gestation (d 65 to 100) were assigned to diets (six per diet) consisting of endophyte-free (E-) or E+ tall fescue seed (50% E- or E+ tall fescue seed, 45% sweet feed, and 10% molasses fed at 1.0% of BW/d). Mares also had ad libitum access to E+ or E- annual ryegrass hay, and were fed diets for 10 d. Following removal from the tall fescue diet on d 11, mares were placed on common bermudagrass pasture and monitored until d 21. Morning and evening rectal temperatures were recorded and daily blood samples were collected for progesterone and prolactin (PRL) analyses, whereas samples for 3,4-dihydroxyphenyl acetic acid (a catecholamine metabolite) analysis were collected on alternate days. For clinical chemistry analysis, blood samples were collected on d 0, 5, 10 and 21. Daily urine samples were collected for ergot alkaloid analysis, and ultrasonography was performed for presence of echogenic material in fetal fluids. Rectal temperatures (E+ 37.76+/-0.03; E- 37.84+/-0.03 degrees C) and serum PRL concentrations (E+ 14.06< or =0.76; E- 12.11+/-0.76 ng/mL) did not differ (P = 0.96) between treatments. Measuring the change in basal serum concentration from d 0 over time, progesterone concentrations did not differ (-0.64 +/-1.49 and -0.55+/-1.47 ng/mL for E+ and E- mares, respectively). There was no negative pregnancy outcome, and ultrasonography indicated no increase in echogenic material in fetal fluids. Plasma 3,4-dihydroxyphenyl acetic acid concentrations decreased (P < 0.05) in E+ compared with E- mares (2.1+/-0.14 and 4.4+/0.43 ng/mL, respectively). Urinary ergot alkaloid concentration was greater (P < 0.01) in mares consuming E+ compared with E- (532.12+/- 52.51 and 13.36+/-2.67 ng/mg of creatinine, respectively). Although no fetal loss was observed during the current study, elevated concentrations of urinary ergot alkaloid were consistent with depressed endogenous catecholamine activity, suggestive of an endocrine disruptive effect of hypothalamic origin.

Metabolomics of fescue toxicosis in grazing beef steers

“…The steers were maintained on their respective pastures for 28 days. At baseline (time 0), 1, 2, 14, and 28 days post pasture assignment, plasma and urine were collected and processed for HRM (Li et al, 2013;Patel et al, 2015), urinary ergot alkaloid analysis (Hill et al, 2000), and plasma and urine catecholamine analysis (Smith et al, 2013;Youngblood et al, 2004). Additional details of these analyses are provided below.…”

“…Thus, EA can potentially decrease appetite and food intake through modulation of the hypothalamic serotonergic tone (Rossi-Fanelli and Cangiano, 1991). Sheep plasma DA levels M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 6 increase (Henson et al, 1987) and plasma 3,4-dihydroxyphenyl acetic acid (DOPAC; a dopamine metabolite) levels in mares decrease (Youngblood et al, 2004) in response to toxic fescue consumption.…”

“…25 cm × 10 mm; Supelco Inc., Bellefonte, PA). The mobile phase (pH 3.65) consisted of monobasic sodium phosphate, octyl sodium sulfate, EDTA, methanol, H 2 O, and trimethylamine (Youngblood et al, 2004).…”

“…Sample processing for catecholamine extraction was adapted from (Youngblood et al, 2004) for plasma and (Smith et al, 2013) for urine. Briefly, for plasma, 50 mg acid activated alumina, 500 µL sample, 500 µL 0.2 M Tris buffer (pH 9.0), and 20 µL of internal standard (epinine, 2 ng) were incubated for 15 min at room temperature on a rocker.…”

Fescue toxicosis

“…One study noted increased early equine embryonic mortality with exposure to E fescue (Brendemuehl et al, 1994), and depressed endogenous catecholamine activity has been observed in mares exposed to E fescue early in gestation (Youngblood et al, 2004). However, other studies have found no increased equine pregnancy loss up to day 300, despite lower progestagen concentrations between gestational days 90 and 120 (Brendemuehl et al, 1996).…”