Reproductive hormonal responses to ergotamine and ergonovine in cows during the luteal phase of the estrous cycle

• Published in: Journal of animal science 1998-05, Vol.76 (5), p.1448-1454
• Main Authors: Browning, R., Jr, Schrick, F. N, Thompson, F. N, Wakefield, T., Jr
• Format: Article
• Language: English
• Subjects: Animal reproduction; Animals; Biological and medical sciences; Cattle; Cattle - blood; Cattle - physiology; Cross-Over Studies; Dinoprost - analogs & derivatives; Dinoprost - blood; Dinoprost - metabolism; Ergonovine - toxicity; Ergotamine - toxicity; Feeding. Feeding behavior; Female; Follicle Stimulating Hormone - blood; Fundamental and applied biological sciences. Psychology; Gonadotropins, Pituitary - blood; Hormones; Luteinizing Hormone - blood; Prolactin - blood; Reproduction - drug effects; Reproduction - physiology; Respiration - drug effects; Seasons; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/1998.7651448x

We conducted research to evaluate whether ergot alkaloids associated with endophyte-infected tall fescue could alter plasma concentrations of hormones important to reproductive function in cows. Six primiparous, estrous-cycling Holstein cows nursing calves received single i.v. injections of ergotamine tartrate, ergonovine maleate, or saline vehicle in a simple cross-over design. Each cow received one compound per estrous cycle, d 15 or 16 after estrus, and all compounds over three estrous cycles. Blood samples were collected at 20-min intervals for 40 min before and 240 min after treatments to assess plasma concentrations of prolactin, LH, FSH, and the response by PGF2alpha metabolite 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM). Ambient temperature and respiratory rates were measured hourly. Ambient temperature averaged 26 degrees C during data collection. Treatment x time was a significant source of variation for respiration rate and plasma concentrations of every hormone evaluated except FSH. Ergotamine elevated (P < .01) respiration rates 2 to 4 h after treatment. Ergotamine and ergonovine reduced (P < .001) plasma concentrations of prolactin for 2 to 4 h after treatment compared to concentrations before treatment. Plasma concentrations of LH were lowered (P < .01) by ergonovine during the 3rd h after treatment and by ergotamine during the 4th h after treatment. Most cows exhibited secretory PGFM responses after ergotamine and ergonovine treatments compared with an absence of a PGFM response in all cows after saline (P < or = .01). Results indicated that ergot alkaloids implicated as causative agents for fescue toxicosis can alter plasma concentrations of reproductive hormones during the late luteal phase of the estrous cycle in cows.