Influence of dietary endophyte-infected (Neotyphodium coenophialum) tall fescue (Festuca arundinacea) seed on fecal shedding of antibiotic-resistance selected Escherichia coli O157:H7 in ewes

¹ USDA-ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927
² USDA-ARS, Southern Plains Agricultural Research Center, College Station, TX 77845
³ Department of Animal Science, University of Arkansas, Fayetteville, AR 72701
⁴ USDA-ARS, Forage Animal Production Research Unit, Lexington, KY 40546
⁵ Department of Animal Science, University of Tennessee, Knoxville, TN 37996

^* To whom correspondence should be addressed. E-mail: mlooper{at}spa.ars.usda.gov.

	Abstract

Objectives were to determine effects of short-term feeding of toxic endophyte-infected (Neotyphodium coenophialum) tall fescue (Festuca arundinacea) cultivar 'Kentucky 31' seed on fecal shedding and intestinal concentrations of E. coli O157:H7, and concentrations of prolactin, cortisol, and NEFA in experimentally-inoculated ewes. Twelve ewes (mean BW = 46 ± 2 kg) were fed a diet containing either high endophyte-infected (HI-E) or low endophyte-infected (LO-E) tall fescue seed for 7 d. Each diet consisted of 50% (as-fed basis) tall fescue seed. Ewes were experimentally-inoculated with antibiotic-resistance selected E. coli O157:H7 on d 1 of feeding treatment, and fecal shedding of inoculated pathogens was monitored daily (d 2 to 6). On d 7, ewes were weighed, euthanized, and tissues and contents sampled from the ileum, cecum, and rectum for quantitative enumeration of E. coli O157:H7. Urine was collected at euthanization to determine total ergot alkaloid concentrations. Ewes fed HI-E had lower (P < 0.001) DMI than ewes fed LO-E (0.8 and 1.6 ± 0.1 kg/d DMI for HI-E and LO-E ewes, respectively); consequently, there was a tendency (P = 0.06) for HI-E ewes to lose 0.3 ± 0.4 kg/d and LO-E ewes to gain 0.2 ± 0.4 kg/d during the 7 d. Urinary ergot alkaloids were increased (P < 0.001) in ewes fed HI-E (47.8 ± 9.4 ng/mg creatinine) than LO-E ewes (6.2 ± 9.4 ng/mg creatinine). Prolactin tended (P = 0.06) to be decreased in ewes fed HI-E (7.2 ± 7.0 ng/mL) compared with LO-E ewes (27.7 ± 7.0 ng/mL). Fecal shedding of E. coli O157:H7 tended (P = 0.06) to be increased in HI-E ewes [5.4 cfu (log₁₀)/g feces] compared with LO-E ewes [4.5 cfu (log₁₀)/g feces]. Population of E. coli O157:H7 in luminal contents from the ileum, cecum, and rectum did not differ (P > 0.36) between treatments. Treatment did not influence (P = 0.30) the occurrence of E. coli O157:H7 in cecal or rectal tissues; however, ileal tissues from HI-E ewes tended (P = 0.12) to have an increased incidence of E. coli O157:H7. Concentrations of NEFA tended (P = 0.12) to be greater in HI-E ewes than LO-E ewes while cortisol was similar (P = 0.49) for HI-E and LO-E ewes. We conclude that short-term feeding of HI-E tall fescue seed may alter concentrations of prolactin and NEFA, and may increase fecal shedding of E. coli O157:H7 in experimentally-inoculated ewes.

Key Words: dry matter intake, Escherichia coli O157:H7, ewes, NEFA, tall fescue