Effect of treatment with an ivermectin sustained-release bolus on productivity of stocker beef calves

• Published in: Veterinary parasitology Vol. 58; no. 1; pp. 75 - 82
• Main Authors: Williams, J.C., Loyacano, A.F., Broussard, S.D., Coombs, D.F.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-05-1995
• Subjects: Animals; CALVES; Cattle; Cattle Diseases - prevention & control; Cattle-Nematoda; Control methods-Nematoda; Controlled release technology; COOPERIA; Delayed-Action Preparations; Feces - parasitology; HAEMONCHUS; IVERMECTIN; Ivermectin - administration & dosage; IVERMECTINA; IVERMECTINE; NEMATODA; OSTERTAGIA; Parasite Egg Count; Seasons; TERNERO; Trichostrongyloidiasis - prevention & control; Trichostrongyloidiasis - veterinary; VEAU; Weight Gain; Controlled release technology; Cattle-Nematoda; Control methods-Nematoda; Ivermectin
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/0304-4017(94)00707-J

Three groups of 30 crossbred beef steers, 8–10 months of age and ranging in weight from 158 to 320 kg, were used to compare effects of treatment with an ivermectin sustained-release bolus or two ivermectin injectable treatments on parasite control and productivity in relation to untreated controls during a 168 day winter-spring grazing period. Each group of 30 consisted of five cattle on each of six separate 1.6 ha pastures. Treatments on Day 0 (12 December) were: Group 1: untreated controls; Group 2: ivermectin injectable at 200 μg kg
−1 bodyweight, s.c., on Day 0 and Day 56; Group 3: ivermectin sustained-release bolus to deliver ivermectin at 12 mg day
−1 over approximately 135 days. All cattle were weighed at 28 day intervals and fecal samples were collected for egg per gram counts (EPG). Geometric mean EPG for Group 3 remained consistently less than 1.0 after Day 0 and were highest (2.4) on Day 168. All group EPG were significantly different (
P<0.01) by Day 56, and EPG of Group 2 had increased to 10.5 following initial treatment and to 42.8 on Day 112. With the exception of a low mean EPG of 6.8 for Group 1 on Day 112, EPG of the group were consistently highest (range 24.9–36.0) to the end of the experiment.
Ostertagia ostertagi was predominant, along with smaller proportions of
Haemonchus placei and
Cooperia spp. Throughout the experiment Group 3 had highest liveweights and gains that were most often different from those of Group 1 at
P<0.01 or greater. Group 2 had a similar advantage over Group 1, but at
P<0.05. On Day 168, Group 3 had liveweight and cumulative gain advantages over Group 2 of 9.3 kg and 10.8 kg, respectively, but these were not significant. Advantages over Group 1 were 31.1 kg and 30.1 kg, respectively.