Efficacy of Morantel Tartrate in a Sustained Release Bolus on the Control of Subclinical Gastrointestinal Parasitism in First-Year Grazing Dairy Replacements

Abstract

Thirty-four heifers (24 Holstein, 8 Ayrshire, 2 Jersey) and 12 Holstein steer calves were grouped into 23 blocks of 2 animals each according to breed, sex, and body weight. Animals in each block were randomly assigned to control or treated groups. The treated group received an anthelmintic bolus containing morantel tartrate before they were permitted access to pasture. A 2.6 ha pasture was divided in half with a double fence; the resulting two pastures had separate feed and water troughs. Steer calves were slaughtered upon termination of the trial to ascertain gastrointestinal parasite burdens. Two worm-free tracer calves were placed on each pasture every 2 mo and slaughtered after 4 wk of grazing to determine parasite infectivity of pastures. Herbage samples were obtained monthly and analyzed for infective larvae. The trial was conducted for 141 d during the grazing season. Treatment resulted in 90% reduction in infective larvae on pasture, 74% reduction in fecal worm-eggs, 91% reduction in adult worm burdens, and a trend toward reduced worm burdens in tracer calves by 52%. An overall average daily gain of .68 and .88 kg was obtained for control and treated animals. Reproductive data for the heifers remaining in the herd from the trial showed that treatment resulted in 44 less days to first breeding.

Effects of ionophore feeding and anthelmintic administration on age and weight at puberty in spring-born beef heifers.

“…Current literature concerning the treatment of replacement heifers with an anthelmintic has produced contradictory results. Block et al (1985) found heifers treated with morantel tartate had increased weight gain and decreased days to conception. Additionally, Zajac et al (1991) found no difference in final conception rates in heifers developed on pasture that were treated with ivermectin at weaning.…”

Internal parasite levels and response to anthelmintic treatment by beef cows and calves.

“…One of the most widespread Beef, Cows, health problems for ruminants on a worldwide basis is the presence of internal parasites (Armour, 1980;Borgsteede and Burg, 1982). The level of infection and its effect on animal performance in the U.S. and Canada has been documented in certain areas by numerous researchers, including Levine and Aves (1956); Zimmerman and Hubbard (1961); Cox and Todd (1962); Jacobson and Worley (1 969); Ferguson et al (1971); Leland et al (1973); Ciordia (1975); Ward et al (1979); Wescott et al (1979); Baker et al (1981); Block et al (1985);Kuhl et al (1985, andKnox (1989).…”