Effect of infestation by nematodes of the family Trichostrongylidae upon the liveweight gain and wool production of young sheep

Abstract

Extract

Much work has been, carried out in New Zealand to ascertain the response in young sheep to drenching with anthelmintics (for review see Whitten, 1954). Clarke & Filmer (1958) have also examined response to drenching in their studies on hogget' ill-thrift. As Whitten (1954) has shown, results of past drenching trials have been extremely variable. In some cases little or no response has been observed, in others considerable increases; in weight gains have been achieved. More recently, Robertson (1963) has summarized the results of part of an extensive series of country-wide post-weaning drenching trials conducted by the Department of Agriculture with the new anthelmintic thiabendazole. In those trials consistent, weight gain responses were recorded in favour of the drenched animals. However, most of the published data are from trials involving strategic drenching programmes designed to control or limit infestation rather than to suppress completely, patent infestation. Most of these trials have been confined to late summer, autumn and winter, and few have attempted to cover the entire first year of young sheep. Furthermore, little attempt has hitherto been made to correlate responses obtained with the changing degree and species composition of infestation throughout the course of the trial.