Bulls grazing Kentucky 31 tall fescue exhibit impaired growth, semen quality, and decreased semen freezing potential
2015
Pratt, S.L. | Stowe, H.M. | Whitlock, B.K. | Strickland, L. | Miller, M. | Calcatera, S.M. | Dimmick, M.D. | Aiken, G.E. | Schrick, F.N. | Long, N.M. | Duckett, S.K. | Andrae, J.G.
Serum prolactin (PRL) and testosterone concentrations, body weight, body composition, semen quality, and semen freezing potential for bulls grazing the toxic tall fescue (Lolium arundinaceum [Schreb.] Darbysh. = Schedonorous arundinaceum [Schreb.] Dumort.) cultivar Kentucky 31 (E+) compared with a novel endophyte cultivar lacking ergot alkaloids (E−) were evaluated. Angus bulls were allotted to treatment (Day 0) and grazed E+ or E− for 155 days. Treatment-by-day interaction was significant (P < 0.05) for serum PRL concentrations with E+treated bulls exhibiting reduced PRL values compared with E− control bulls, but no differences were observed for serum testosterone concentrations (P > 0.05). Further, bulls on the E+ treatment exhibited decreased total gain, average daily gain, and body weight by Day 140 (P < 0.05) compared with the E− bulls. Rump muscle depth was lower because the treatment in bulls grazing E+ compared with E− (P < 0.05) and intramuscular fat in the E− bulls compared with the E+ group was higher by Day 155 (P < 0.05). Analysis of ejaculates showed significant treatment × day effects for sperm concentration with lower values observed for bulls on the E+ treatment (P < 0.05). The percent normal morphology was reduced in ejaculates from E+ bulls compared with E− bulls (P < 0.05), and the difference was due to an increase in abnormal sperm present in the E+ ejaculates from Day 84 to 140 (P < 0.05). In addition, spermatozoa motility and progressive motility were decreased on thawing in semen samples from E+ bulls compared with E− bulls (P < 0.05).
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