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1 Oregon State University, College of Veterinary Medicine, Corvallis 97331
* To whom correspondence should be addressed. E-mail: A.Morrie.Craig{at}oregonstate.edu.
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Abstract |
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The digestive responses and degradation of ergovaline and production of lysergic acid in the rumen of sheep offered Neotyphodium coenophialum-infected tall fescue straw at 2 ergovaline levels were investigated. Six crossbred wethers (56 ± 3.0 kg BW) were used in a randomized crossover design involving 2 treatments, for a total of 6 observations per treatment. The experiment consisted of two 28-d feeding periods with a 14-d washout period between them. Treatments were: 1) tall fescue straw containing < 0.010 mg/kg ergovaline (E-), and 2) tall fescue straw containing 0.610 mg/kg ergovaline (E+). Feed, orts, and feces were measured and analyzed for DM, ADF, and CP, and used to determine digestibilities. Feed and water intake were monitored throughout the feeding periods. Body weight and serum prolactin levels were measured at the start and end of each feeding period. Ruminal fluid was sampled 3 times (d 0, 3, and 28) during each 28-d feeding period for ergovaline, lysergic acid, ammonia, and pH. Samples were collected at 0 (prior to feeding), 6, and 12 h after feeding. Total fecal and urine collection commenced on d 21 and continued until d 25 of each feeding period. Ruminal ammonia, ruminal pH, and rectal temperature were not influenced by ergovaline concentration (P > 0.10). Digestion of DM, ADF and CP were not different between treatments (P > 0.10). Daily water intake was less for the E+ diet (2.95 vs. 2.77 L/d ; P < 0.05) as was serum prolactin (22.9 vs 6.4 ng/mL; P < 0.05). Ergovaline concentration in ruminal fluid increased over sampling days at each sampling time (P < 0.05). Lysergic acid concentration in ruminal fluid increased over time from d 0 to 3 (P < 0.05) but was not different between d 3 and 28 (P > 0.10). In the E+ treatment, ergovaline was not detectable in the urine, whereas the concentration in the feces was 0.480 mg/kg. Lysergic acid was detected in the diet of the E+ treatment at 0.041 g/kg, lysergic acid in the urine was 0.067 mg/kg, and in the feces was 0.102 mg/kg. The apparent digestibility of the alkaloids was 64.2% for ergovaline and -12.5% for lysergic acid. Approximately 35% of dietary ergovaline and 248% of dietary lysergic acid were recovered in the feces and urine. The appearance of lysergic acid in the feces, urine, and ruminal fluid is likely due to microbial degradation of ergovaline in the rumen and further break down in the lower digestive tract.
Key Words: endophyte, ergovaline, lysergic acid, ruminants, sheep, tall fescue
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