This study assessed the effects of fescue toxicosis on ruminal metabolism and physiology in steers. Twelve ruminally cannulated Angus steers [body weight (BW) = 547 ± 9 kg] were blocked by BW and randomly assigned to six blocks. The steers were fed alfalfa cubes (1.5× NEm) and dosed (1 kg/d) with either endophyte-infected tall fescue seed (E+) or endophyte-free tall fescue seed (E-) via rumen cannula for 21 days. Ruminal dry matter (DM) content was tended to have a higher (p=0.052) in steers in E+ than in E- group. Total volatile fatty acid (VFA), acetate concentrations, as well as the acetate:propionate ratio, were higher (p=0.084, 0.095, and <0.001, respectively) in the E+ group, while propionate was lower (p<0.001). Ruminal pH and temperature were similar between treatment groups (p=0.62 and 0.95, respectively), but ruminal pressure was higher (p<0.001) in E-. Additionally, serum prolactin levels was lower (p<0.001) in the E+ group. These findings suggest that consumption of endophyte-infected tall fescue seed may impair ruminal VFA absorption, potentially due to changes in ruminal motility.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Animals, treatments, and feeding
    2. Ruminal fluid collection
    3. Blood collection
    4. Rumen evacuation, and ruminal pH, temperature andpressure measurement
    5. Fescue seed and diet analysis
    6. Statistical analysis
Ⅲ. RESULTS AND DISCUSSION
Ⅳ. CONCLUSIONS
Ⅴ. ACKNOWLEDGMENTS
Ⅵ. REFERENCES

• Do Hyung Kim(Department of Animal Science, Gyeongbuk Provincial College, Yecheon 36830, Korea) Corresponding author
• Ki-Won Lee(Grassland & Forages Division, National Institute of Animal Science, RDA, Cheonan 31000, Korea)