Authors : R. C. Seals, G. M. Schuenemann , . W. Lemaster , A. M. Saxton , J.C. Waller and F. N. Schrick
Abstract: An experiment was performed in heifers to determine whether consumption of ergotamine tartrate to simulate fescue toxicosis altered ovarian dynamics associated with grazing endophyte-infected tall fescue. Sixteen heifers received corn silage topdressed with a 2:1 supplement of ground corn:soybean meal, and either 0 (CON; n = 8) or 34 g/kg body weight of ergotamine tartrate daily (TRT; n = 8) mixed within the supplement. Heifers were monitored weekly for changes in body weight gain and content of ergotamine tartrate adjusted accordingly. During a 30-d adjustment period to assigned diets, estrus was synchronized and all ovarian structures were recorded daily by transrectal ultrasonography for one estrous cycle. Heifers were bled daily by jugular venipuncture for determination of progesterone, estradiol-17$, FSH and prolactin concentrations. Neither ADG nor concentrations of progesterone, estradiol and overall FSH differed between treatments during the estrous cycle. Concentrations of prolactin were lower in TRT (141 ? 16 ng/ml) than in CON heifers (174 ? 16 ng/ml; P < 0.01). Estrous cycle length was longer in TRT heifers (21 ? 0.6 d) than CON heifers (19.7 ? 0.7 d; P < 0.05). Total numbers of follicles > 5mm, and age and diameters of the F1 and F2 follicles of each corresponding wave did not differ between treatments. Age and size of the ovulatory follicle of TRT heifers were not different from CON heifers. In conclusion, ovarian dynamics were not affected in heifers consuming ergotamine tartrate, suggesting that oocyte maturation or either the oviductal or uterine environments may be involved in reduced embryo development associated with consumption of ergotamine tartrate.
Seals, R. C. , G. M. Schuenemann , . W. Lemaster , A. M. Saxton , J.C. Waller and F. N. Schrick , 2005. Follicular Dynamics in Beef Heifers Consuming Ergotamine Tartrate as a Model of Endophyte-infected Tall Fescue Consumption . Journal of Animal and Veterinary Advances, 4: 97-102.