Epidemiology and control of gastrointestinal parasitism in grazing cattle in Missouri
DOI:
https://doi.org/10.21423/bovine-vol1984no19p208-212Keywords:
animal parasitic nematodes, Anthelmintics, benzimidazoles, DRUG THERAPY, epidemiology, fenbendazole, Helminthoses, helminths, infections, nematode infections, parasites, parasitosesAbstract
The derivation of a method using resident and tracer calves to determine whether or not Ostertagia ostertagi had arrested its development in cattle during the summer is described. Application of this method to the O. ostertagi population in calves in Missouri, USA, during winter 1980-81 showed insignificant numbers of arrested 4th-stage larvae. In late April 1981 herbage larval counts of pasture idle since December 1980 showed high levels of infective O. ostertagi larvae. Pasture larval counts declined steadily during the summer while in calves the number of arrested 4th-stage larvae significantly increased from April to August. Parasitized calves theoretically gained 0.2 kg less/day than control calves and the decrease in weight gain strongly correlated with resumption of the development of arrested larvae. A repeat study the following year produced similar results. Calves of cows given 10 mg/kg body weight fenbendazole just after calving had gained significantly more weight than calves of untreated cows by the beginning of July. The calves were also given fenbendazole (5 mg/kg) 3 weeks later (July 19) and by weaning had a 22.5 kg advantage over untreated calves, thus restoring about 75% of the weight lost through parasitism. Recommendations for deworming procedures are made.
