The impact of internal parasites on cattle production systems varies greatly throughout Australia. Generally however, it is cost effective to treat internal parasites in susceptible stock to prevent sub-clinical production losses, particularly in the more intensive grazing management systems of the southern temperate zones. Targeted use of chemicals still provides the backbone of control programs, but the need to integrate non-chemical control methods (in the face of decreasing gross margins and potential chemical resistance) can help improve profitability and prolong the efficacy of current drench groups. In the tropical north, three worm types, Haemonchus placei (the cattle Barber's Pole), Cooperia punctata and Cooperia punctinata have the potential to cause production losses. Recent worm testing results in northern Australia has also shown other worm species present including surprising numbers of Ostertagia (the Small Brown Stomach Worm). Losses in production tend not to be measured in livestock deaths per se, but as the sub-clinical, insidious loss of potential weight gain. Young stock (being the most susceptible) are unable to mount effective immune responses and nutrients normally used for growth are diverted to help counter parasite infestations.
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