OBJECTIVE-To evaluate the effect of parenteral administration of ivermectin and erythromycin on abomasal emptying rate in suckling calves. ANIMALS-6 male Holstein-Friesian calves < 15 days old. PROCEDURES-In a crossover study, calves were administered each of 3 treatments (control treatment, 2 mL of saline [0.9% NaCl] solution, IM; erythromycin, 8.8 mg/kg, IM; and ivermectin, 200 microg/kg, IV). Thirty minutes later, calves were bottle-fed 2 L of fresh cow's milk containing acetaminophen (50 mg/kg). Blood samples were collected from a jugular vein at various periods after suckling of milk. Abomasal emptying rate was assessed by use of the time to pharmacokinetically determined maximal plasma acetaminophen concentration. RESULTS-Administration of erythromycin and ivermectin caused a significant increase in abomasal emptying rate, compared with results for the control treatment, as determined on the basis of time to maximal plasma acetaminophen concentration. CONCLUSIONS AND CLINICAL RELEVANCE-Parenteral administration of erythromycin and ivermectin increased the abomasal emptying rate. The macrolide erythromycin can be an effective prokinetic agent in calves and other animals. Ivermectin is classified as a macrolide but has a number of structural differences from erythromycin. The clinical importance of a slight increase in abomasal emptying rate after IV administration of ivermectin remains to be determined because ivermectin is only labeled for SC, oral, and topical administration.

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Several conditions may lead to obstruction of the flow of ingesta through the intestinal tract(2,6). Mechanical accidents such as intussusception, volvulus, and strangulation, in which there is a physical occlusion of the intestinal lumen (1,2,4,6). Functional obstructions, such as those which occur with local or general paralytic ileus may mimic mechanical problems.(2,4,6). Congenital malformations may include atresia or constriction of portions of the gut and has been reported in calves and lambs(2,4,6). Compression stenosis by blood clot from an expressed corpus luteum site on an ovary, or traumatic duodenitis caused by migration of a metallic foreign body(2,5). Intestinal carcinoma occurs very rarely in cattle(6). External pressure by mesenteric fat necrosis is a condition of cattle in all dairy, breeds(2,6). Luminal blockages occurs by phytobezoars, and trichobezoars(2,3). The clinical signs of these conditions include a reduction in the amount or a failure to pass feces, progressive abdominal enlargement and colic (2,6).