Evaluation of Domperidone Dosages and Delivery Methods for the Treatment of Fescue Toxicosis in Beef Heifers 1

The objective of this study was to develop a practical method of domperidone delivery to ameliorate fescue toxicosis. Experiment 1 used heifers assigned to 7 treatment groups (n = 6 each): positive control (0.44 mg domperidone/kg BW daily s.c. for 9 d), negative control, and 0.22, 0.44, 0.88, and 1.76 mg domperidone/kg BW per os daily for 9 d, or a 3 g domperidone i.m. injection. Blood was collected every third day for 24 d. Domperidone concentrations in the 0.88 and 1.76 mg/kg BW treatments and the i.m. treatment were greater than positive control (P < 0.05) on d 3. None of the oral treatments were greater than the positive control on subsequent days. Between d 6 and 24, no oral treatments differed from the negative control except for the 1.76 mg/kg of BW treatment on d 9. The i.m. formulation increased domperidone when compared with the negative and positive controls (P < 0.05) on d 3 through d 21. Experiment 2 evaluated the i.m. injection protocol on performance. Heifers were assigned to control (n = 15) or i.m. domperidone (n = 15) treatments and grazed endophyte-infected fescue paddocks. Blood was sampled weekly and analyzed for progesterone and prolactin concentrations. Controls had reduced BW gains (P < 0.001) and BCS (P < 0.05) and elevated rectal temperatures (P < 0.05) compared with treated heifers. Domperidone treatment interacted with day on affecting prolactin (P < 0.0001) and progesterone (P < 0.0001). Intramuscular delivery of domperidone is an effective method for relieving fescue toxicosis.