Influence of rumen fermentation on response to endophyte-infected tall fescue seed measured by a rat bioassay.
Possible alteration of toxicity of endophyte-infected tall fescue by ruminal fermentation was studied using 28 Harlan Sprague-Dawley rats (avg. initial wt., 141 g). These were assigned randomly to one of four treatments in a 2*2 factorial consisting of a 14-day growth period with weights and feed consumption data determined on days 0, 5, 10 and 14. Treatments were: endophyte-infected Kentucky-31 tall fescue seed (E+) or endophyte free Johnstone tall fescue seed (E-) that was incubated for 0 (NON) or 24 hours (INC) with rumen fluid collected from a 290-kg cannulated steer fed a diet containing 37% endophyte-infected tall fescue hay. Diets consisted of 50% lab chow, 39% fescue seed and 11% rumen contents (air-dry basis). Alkaloid content (N-acetyl plus N-formyl loline) for the four diets were 2540, 2680, 0, and 0 micrograms/g for E+NON, E+INC, E-NON, and E-INC diets, respectively. E- treatments gained faster, consumed more feed and converted feed more efficiently (P < .05) than did E+ fed groups. No difference in feed intake was observed within E+ treatments, however, the E+INC diet gained faster (P < .05) and converted feed more efficiently (P < .05) than did E+NON fed rats (2.56 vs 1.96 g/d and 5.94 vs 7.51 g of feed/g of gain for gain and feed conversion, respectively). Including endophyte-infected seed in rat diets depressed performance (ie. intake, gain and feed efficiency). This depression was partially alleviated by a 24-hour incubation with rumen fluid contents suggesting that toxicity of endophyte-infected tall fescue is lessened due to rumen microbial action.
Westendorf
M L
ML
Department of Animal Science, University of Kentucky, Lexington 40546-0215.
Mitchell
G E
GE
Tucker
R E
RE
D000164:Acremonium / Q000254:growth & development*; D000469:Alkaline Phosphatase / Q000097:blood; D000470:Alkaloids / Q000506:poisoning; D000818:Animals; D001681:Biological Assay; D001835:Body Weight; D004435:Eating; D005285:Fermentation; D008297:Male; D006109:Poaceae / Q000382:microbiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012417:Rumen / Q000378:metabolism*
D000470:Alkaloids; D000469:Alkaline Phosphatase