Development of a "Wapiti Score" visual assessment tool for determining introgression of wapiti genes in young red deer.
Red deer are the predominant farmed breed type in New Zealand, but crossbreeding red females with wapiti (or elk) males in a terminal sire system is common. Introgression of wapiti genes into the national red deer breeding hind herd has been shown to have a negative impact on the pregnancy rate of 16-18 month old hinds. We devised a four point visual scoring system (Wapiti Score), based on wapiti phenotype characteristics for application to weaner (6-10 month old) red deer, to allow rapid detection of wapiti introgression. This scoring system was trialled and refined using 449 rising 1-year-old red deer of mixed genotype and sex on a commercial breeding and finishing farm during three pelage phases. For a subset of 186 animals, Wapiti Score was compared with the DNA based GenomnzTMGenometerTM G3 Hybrid Test Estimated Elk (EstElk), where EstElk is the estimated proportion of wapiti (elk) genes in an individual animal predicted by the GenometerTM. A significant positive correlation (P<0.05) was found between EstElk and Wapiti Score for two independent observers, with an increase of 1 point in Wapiti Score corresponding to an increase of ∼0.10 in EstElk. The strongest correlation between Wapiti Score and EstElk were from the winter and spring scores. The effectiveness of Wapiti Score as a tool for classifying young deer by breed-type (red deer or wapiti) was assessed using 0.2 EstElk as the breed-type threshold and comparing that against different selection Wapiti Scores (1-3). It is suggested that the adoption of WS technique will allow farmers to make objective decisions on genetic management at an early age; and that this will be reflected in improved pregnancy rates for New Zealand yearlings.