Observations on the phenotypic relationships between anti-CarLA salivary IgA antibody response, nematode infection levels and growth rates in farmed red (Cervus elaphus) and wapiti hybrid deer (Cervus elaphus canadensis).

Nematode parasites are one of the most significant production limiting factors in farmed deer in New Zealand. One long term strategy to reduce reliance on anthelmintics is to select deer that develop resistance to parasites. It has been shown in sheep that secretory antibody (IgA) in the saliva against a Carbohydrate Larval Antigen (CarLA) on infective larvae (L3) of a wide range of gastro-intestinal nematodes protects against reinfection. This paper describes a longitudinal slaughter study undertaken to measure anti-CarLA IgA antibody (CarLA-IgA) levels in the saliva of 5-12 month old farmed red and wapiti-cross-red deer (wapx) grazed together and to attempt to relate these levels to parasite burdens and productivity. The study showed that salivary CarLA-IgA levels peaked in June (late autumn) and October (mid spring), but the levels in wapx deer were significantly lower than in red deer. Over the May-December period 55% of red deer had CarLA-IgA values ≥2 units compared with 26% of wapx deer and over this period red deer had consistently lower adult abomasal parasite burdens than wapx deer. The average number of adult abomasal nematodes was significantly lower at each slaughter from May to December for all deer with CarLA-IgA ≥2 units vs <2 units. There were no demonstrable correlations with liveweight gain in these small groups of deer.