Graduate Thesis Or Dissertation
 

Metabolism of ergot alkaloids by sheep

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  • The digestion responses and degradation of ergovaline and production of lysergic acid in the rumen of sheep offered Neotyphodium coenophialum-infected tall fescue straw at two ergovaline levels was investigated. Six crossbred wethers (56 +1- 3 kg BW) were randomly assigned to one of two treatment groups in a cross-over design. Each experimental period consisted of 28 d feeding periods with a 14 d wash-out between periods. During the wash-out period all animals received a diet containing <10 ppb ergovaline. Treatments were 1) < 10 ppb ergovaline (E-) and 2) 500 ppb ergovaline (E+). Ergovaline levels were achieved with a combination of tall fescue straw (35Oppb ergovaline) plus Neotyphodium coenophialum-infected tall fescue seed (3,300 ppb ergovaline). Diets were isonitrogenous. Rumen fluid was sampled three times (d 0, 3, 28) during the 28- day experimental period for ergovaline and lysergic acid. Samples were collected at time 0 (prior to feeding), 6, and 12 h post feeding. Total fecal and urine collection commenced on d 21 and continued till d 25 of the experimental period. Rumen ammonia, rumen 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). Feed intake and body weight were different between treatments (P> 0.10). Water intake was reduced by ergovaline intake (P <0.05). Serum prolactin was reduced by 27% with ergovaline intake (P <0.05). Ergovaline concentration in rumen fluid expressed as a percent of intake increased over sampling time and sampling day (P < 0.05). Lysergic acid concentration in rumen fluid expressed as a percent of intake increased over time from dO to d3 (P < 0.05) but was not different between d3 and d28 at any time point (P> 0.10). The feces contained an average of 0.41 tmo1/day ergovaline and 0.87 μmol/day lysergic acid. Urine contained no detectable ergovaline; lysergic acid concentration was 1.05 μmol/day The appearance of lysergic acid in the feces, urine and rumen fluid is likely from the degradation of ergovaline in the rumen due to microbial degradation and further break down in the lower digestive tract. In order to determine if the increased tolerance sheep display to fescue toxicosis is due to ruminal bacteria five major sheep ruminal bacteria were monitored during the adaptation to Neotyphodium coenophialum -infected tall fescue straw. This increased tolerance supports the belief that there are microorganisms in the rumen of sheep capable of detoxifying the alkaloids found in infected tall fescue. Rectal temperatures and serum prolactin levels were monitored as an indication of toxicosis. Daily rectal temperatures were not influenced by alkaloid concentration (38.4°C E- vs. 38.4 °C E+, SE 0.0615; p = 0.40). Serum prolactin was decreased to 6.4 ng/ml for E+ from 22.9 ng/ml for Etreatment (SE 5.19; p = 0.023), indicating subclinical but not clinical fescue toxicosis. A period effect was detected for most primers used, indicating change in microbial populations due to adaptation to the fescue straw. Prevotella bryantii B14 was detected in low levels through the entire feeding period and levels were approximately the same (95% B- and 89% E+ of day 0 on day 28) from day 0 to 28 but no difference was detected between treatment groups (90% E- vs. 93% E+; p = 0.45). The Streptococcus group (S. bovis, S. caprinus, S. equines) was detected in low levels through the entire feeding period and E+ treatment tended to lower the concentration of 16S gene but no statistical difference was detected between treatment groups (89% E- vs. 94% E+; p = 0.39). Selenomas ruminantium- Mitsuokella multiacida JCM6582 was the most abundant organism found in the samples and levels were approximately the same (97% E- and 105% E+ of day 0 on day 28) from day 0 to 28 but no difference was detected between treatment groups (92% E- vs. 106% E+; p = 0.52). Eubacterium ruminatium (ATCC 17233) was undetectable in most samples over all periods. Ruminococcus flavefaciens (ATCC 19208T) sequence was detected in moderate levels through the entire feeding period and levels were approximately the same (97% E- and 99% E+ of day 0 on day 28) from day 0 to 28 but no difference was detected between treatment groups (91% E- vs. 92% E+; p = 0.28). Ruminococcus albus was detected in low levels through the entire feeding period and levels were approximately the same (95% E- and 83% E+ of day 0 on day 28) from day 0 to 28 but no difference was detected between treatment groups (87% E- vs. 89% E+; p = 0.33). These results imply that none of the five bacteria monitored in this study is responsible for the metabolism of ergot alkaloids.
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