| Autor: |
A F, Koontz, L P, Bush, J L, Klotz, K R, McLeod, F N, Schrick, D L, Harmon |
| Rok vydání: |
2011 |
| Předmět: |
|
| Zdroj: |
Journal of animal science. 90(3) |
| ISSN: |
1525-3163 |
| Popis: |
Tall fescue (Lolium arundinaceum) toxicosis research is often complicated by a reduction in intake of infected forage or seed, making treatment comparisons difficult. This study was conducted to develop a fescue toxicosis model that would allow for variations in DMI without altering the quantity of alkaloids consumed over the course of the experiment. Ground tall fescue seed and a tall fescue seed extract were used in two 2-period crossover experiments to determine the effectiveness of ruminal dosing of a tall fescue seed extract to induce fescue toxicosis. This experiment used 4 growing Holstein steers (BW = 337 ± 24 kg) surgically fitted with ruminal cannulas. Steers were maintained on a diet of endophyte-free fescue hay fed ad libitum throughout the experiment. Endophyte-infected (E+; 4.1 mg/kg of ergovaline) and uninfected (E-; 0.0 mg/kg of ergovaline) KY-31 tall fescue seed was ground and dosed or extracted with ethanol, concentrated, and lyophilized before ruminal dosing. Ergovaline concentration of the final extract was 102 mg/kg. Animals were given a minimum of a 3-wk washout period between treatments. Physiological indicators were measured over 7 d at 22°C (d 1 to 3) and 32°C (d 4 to 7) during both seed and extract dosing. Seed and extract E+ dosing reduced serum prolactin concentrations such that they were not different from zero (P0.10). Treatment with E+ reduced feed intake (P0.05) and heart rate (P0.001), and increased respiration rate (P0.01) and core temperature (P0.05) during both seed and extract dosing. Increasing environmental temperature from 22 to 32°C reduced total intake (P0.05) and increased core temperature (P0.001) and respiration rate (P0.001) during both seed and extract dosing. Diastolic blood pressure tended (P0.09) to be increased during E+ extract dosing and reduced during heat stress. These physiological alterations are consistent with those reported for cattle grazing or consuming seed from endophyte-infected tall fescue. These data indicate that a ruminally dosed ethanol extract of tall fescue seed is efficacious in inducing fescue toxicosis in cattle. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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