Evaluation of cross-grazing deer with sheep or cattle, as means to reduces anthelmintic usage to control gastrointestinal and pulmonary nematodes in farmed red deer (Cervus elaphus) in New Zealand

Abstract Recent reports indicate that gastrointestinal nematodes (GIN) are contributing to significant losses in deer productivity and that anthelmintic resistance has become an issue of concern for deer farmers in New Zealand. The aim of this study was to evaluate cross-grazing of deer with sheep or cattle as an aid for control of gastrointestinal and pulmonary nematode parasites of farmed red deer (Cervus elaphus) in New Zealand. This was a field study replicated over two years (2012 and 2013) for 16 weeks each year at two locations (Massey University, Palmerston North and Invermay AgResearch Centre, Mosgiel). Each farm replicate included four groups (19–20 deer) at each location: red deer cross-grazing with cattle (Deer/Cattle); red deer cross-grazing with sheep (Deer/Sheep); red deer grazing on their own (DeerOwn); and red deer grazing on their own and treated with anthelmintics every two weeks to suppress worm burdens, as a positive control (DeerSup). The key outcome was the number of anthelmintic treatments (AT) given to deer. The decision to treat individual resident deer in Deer/Cattle, Deer/Sheep and DeerOwn groups was based on “trigger” criteria including faecal egg count (FEC)≥250 eggs/g or Dictyocaulus faecal larval count (FLC)≥100 larvae/g or when growth rate was less than 80 % of the mean of the DeerSup group in the previous two weeks. In addition, to quantify the species of parasites cycling in each group, sets of three “tracer” deer were introduced to graze with each group at the mid-point and again at the end of each 16 week period in both years at both locations. Least squares means (LSM) of the number of AT given per animal for Deer/Sheep (3.4) and DeerOwn (3.3) groups were significantly higher than for the Deer/Cattle (2.7) group (p 0.05). The LSM of lungworm were fewer in Deer/Sheep (3), Deer/Cattle (4) and DeerSup (3; p