DOES RECTAL PALPATION OF PREGNANT MOOSE COWS AFFECT PRE- AND NEO-NATAL MORTALITY OF THEIR CALVES?
Chemical immobilization and handling of animals may increase the risk of mortality and reduce reproductive output and survival of offspring born to immobilized mothers. We examined to what extent winter chemical immobilization using etorphine and subsequent handling affected the immediate risk of mortality and subsequent calving success and early calf mortality in a Norwegian moose population. Following 227 immobilizations of 136 different moose, we experienced no mortality during the capture process or any mortality in the 6 weeks following immobilization. Similarly, there were no significant differences in calving success (presence or absence of calf or calves) or summer mortality (birth – mid-September) of calves from cows drugged the preceding winter versus undrugged cows. However, splitting the material into age groups, we found significantly lower calving success among drugged cows aged 6-15-years compared to un-drugged cows of the same age group, and higher mortality of calves born to 4-year-old drugged cows compared to those from 4-year-old un-drugged cows. Cows that were rectally palpated for pregnancy determination had a higher fetal and calf loss than those that were not rectally palpated. This led us to conclude that rectal palpation, and not the immobilization process per se, was the most likely cause of reduced calving success and calf survival. The presence of a palpation effect may have been influenced by increased stress involved with the weighing process to obtain body mass, but nearly all cows were weighed after immobilization, so we were unable to determine the separate effect of this procedure.
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