Reproductive hormonal responses to ergotamine and ergonovine in cows during the luteal phase of the estrous cycle.
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.
Browning
R
R
School of Agriculture and Home Economics, Tennessee State University, Nashville 37209, USA.
Schrick
F N
FN
Thompson
F N
FN
Wakefield
T
T
D000818:Animals; D002417:Cattle / Q000097:blood* / Q000502:physiology; D018592:Cross-Over Studies; D015237:Dinoprost / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism; D004874:Ergonovine / Q000633:toxicity*; D004878:Ergotamine / Q000633:toxicity*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D011388:Prolactin / Q000097:blood; D012098:Reproduction / Q000187:drug effects / Q000502:physiology*; D012119:Respiration / Q000187:drug effects; D012621:Seasons
D006065:Gonadotropins, Pituitary; C008228:15-keto-13,14-dihydroprostaglandin F2alpha; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D015237:Dinoprost; D004878:Ergotamine; D004874:Ergonovine