A survey of internal parasites and parasite control on North Island deer farms

Aim. To evaluate internal parasite control practices and their effectivenes s, and to investigate relationships between indices of parasitism and produ ction outcomes by analysis of data collected during a deer herd health and production profiling project. Methods. A longitudinal study of 15 red deer farms in the North Island of N ew Zealand was carried out from March 1992 to April 1994. Anthelmintic usag e was recorded. Sentinel weaner, yearling and adult hinds and stags were bl ood and faecal sampled in early autumn, winter, spring and summer for serum pepsinogen and faecal egg and larval counts. A descriptive analysis of con trol programmes and egg and larval counts was produced. In addition, furthe r measurements of parasitism and parasite control, including faecal egg cou nt and faecal larval count data, individual pepsinogen concentrations, timi ng and numbers of anthelmintic treatments, and a farm calf faecal lungworm larvae count index were firstly subjected to univariate statistical associa tion with production outcomes, followed by stepwise multivariable logistic regression analysis. Timing and numbers of anthelmintic treatments, along w ith other farm, herd or animal management risk factors, were included into path models. Results. A wide range of anthelmintic programmes in all age groups, within farms between years and between farms was recorded. Weaner deer received th ree to nine treatments in their first year. Many farmers treated older deer in only one of the years of study. Older stags were treated more often tha n younger stags. Oxfendazole, ivermectin and moxidectin were the most commo nly used anthelmintics. Egg and larval counts varied between properties and between years in some seasons but a higher proportion of deer shed larvae than eggs. In winter the number of weaners shedding eggs was the same as in autumn, but fewer shed lungworm larvae. Counts were lower at 12 months of age. Counts in older stags and hinds were highest in early spring, and coun ts were higher in yearling stags than in adult staffs. Geometric mean pepsi nogen concentration was lowest in weaners and rose to adult levels by early spring. Statistical analyses showed a lower weaning weight associated with higher faecal larval count index, and a reduced number of anthelmintic tre atments prior to weaning. Weaners grew faster in spring after late winter a nthelmintic treatment than those without treatment or with later treatments . There were inverse relationships between both farm mean weaner and adult serum pepsinogen and summer,growth of weaners, and weaning percentage of ad ult hinds, respectively. Conclusion. This study has highlighted current parasite control practices, relationships between indices of parasitism and production outcomes, and ha s identified areas for further research into parasitism in farmed deer. Key words. Deer, parasite control, egg counts, larval counts, multivariable an alysis.