Effects of metoclopramide on steers grazing endophyte-infected fescue.
The dopamine antagonist metoclopramide (MC) was administered to steers grazing on endophyte-infected fescue. Yearling Angus steers (n = 24) were assigned randomly to pasture treatments including high (74%) and low (33%) endophyte levels and low (134 kg N.ha-1.yr-1) and high (335 kg N.ha-1.yr-1) N fertilization rates. One steer of the pair in each paddock (n = 12) received MC, whereas the other received sucrose (S) (15 mg/kg body weight, orally, three times a week for 10 wk). Blood for basal and maximal TRH-stimulated serum prolactin (PRL) concentrations was obtained before animals grazed fescue, after grazing for 1 mo, and after 3, 6 and 9 wk of animal treatment. Grazing endophyte-infected fescue decreased (P less than .05) basal serum PRL concentrations (less than 1.0 vs 5.3 ng/ml, high vs low endophyte). Basal serum PRL increased after 3, 6 and 9 wk of MC treatment (58.1 vs 5.4, 46.0 vs 12.0 and 50.8 vs 16.9 ng/ml, MC vs sucrose, respectively). After 6 wk of animal treatments, MC increased (P less than .05) serum cholesterol (84.7 vs 60.8 mg/dl, MC vs S). Animals treated with MC spent more (P less than .05) time between 1200 and 1600 grazing (22.4% vs 6.2%, MC vs S respectively) and had faster ADG (.314 vs .150 kg/d, MC vs S). The results implicate dopaminergic processes in fescue toxicosis.
Lipham
L B
LB
Dept. of Physiol. and Pharmacol., College of Vet. Med., University of Georgia, Athens 30602.
Thompson
F N
FN
Stuedemann
J A
JA
Sartin
J L
JL
D000164:Acremonium / Q000502:physiology*; D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000097:blood*; D013006:Growth Hormone / Q000097:blood; D007328:Insulin / Q000097:blood; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology*; D006109:Poaceae / Q000382:microbiology*; D011388:Prolactin / Q000097:blood; D011897:Random Allocation; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism; D013997:Time Factors
D007328:Insulin; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013006:Growth Hormone; D008787:Metoclopramide