The effect of ivermectin on reindeer offspring's weight gain and survival: preliminary findings

F a w n survival is a central issue for Scandinavia's reindeer industry. Nonetheless, there has been m i n i m a l research conducted on parasitism's effect on reproductive success of female reindeer and their abi l i ty to foster viable offspring to weaning. Investigation of the ecological relationship between parasitism and host fitness, as w e l l as the economic and veterinary medical importance of anthelmintic treatment, is faciliated by conducting field trials i n w h i c h animals treated w i t h anthelmintic are compared to nontreated controls. W e are presently conducting a randomized field tr ial to explore the effects of ivermectin treatment on pre-reproduc¬ tive and mature female reindeer. O u r p r imary response variables include age at first reproduct ion , and offspring survival and weight. F i n dings w i l l provide fundamental informat ion required for the development of an opt imal parasite treatment strategy w h i c h aims at m i n i m i z i n g parasite transmission and maximizing meat product ion. The possible long-term negative side effects of ivermectin are also being explored. O n a theoretical level, project result could elucidate the effects of the general parasite c o m m u n i t y on herd populat ion dynamics and provide data for the study of various quantitative genetic relationships in reindeer. N i e m i n e n (1989) found that offspring of ivermectin-treated females at Kaamanen Reindeer Research Station, F i n l a n d , had a significant 0.5 kg increase (p S 0.05) in average live b i r th weight and a non-significant 2.1 kg increase (p > 0.05) in average autumn live weight . 1 H o w e v e r , our pre l iminary findings indicate that ivermectin treatment of females induces no significant or consistent increase i n m i d to latesummer fawn live weight in coastal N o r t h e r n N o r w a y . This discrepancy f rom the F i n n i s h results may be explained by several factors, among w h i c h sample size or differences in parasite abundance are l i k e l y candidates. The response variable that showed the strongest treatment effect in our pre l iminary results was fawning percent. 2 Ivermectin treated females had a 9 % higher fawning rate (64 % vs. 55 %) than control females, although the difference was not statistically significant (Fisher's Exact Test, p = 0.15; n = 180). We calculated the statistical significance from the means and S.E. published in Poromies-Lehti. 3/1989. Fawning percent is defined as the proportion of research females that was accompanied by a fawn during the time of summer sampling. Rangif er, Special Issue N o . 5, 1990 15

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