Model for predicting 90Sr levels in mule deer

A model was developed to estimate the strontium-90 levels in male mule deer (Odocoileus hemionus hemionus) from known 90Sr intake rates. The model was formulated on results from a study on the effects of age and season on Sr kinetics in mule deer. Captive deer of various ages, at selected times throughout the year, were given acute oral doses of 85SrCl2 and whole body counted to determine the retention function. A two-component exponential equation was used to mathematically describe the retention of 85Sr. The average for the slopes of the short component (1.09 day-1) corresponded very closely with the mean retention time for insoluble material in the gastrointestinal tract. For male deer, the value of the fractional intercept of the long component generally increased with age. The fractional intercepts also varied with the time of year the deer was administered the 85Sr, ranging from an average of 0.0539 during antler dormancy to 0.154 during periods of antler growth. The average of the observed values for the slope of the long component was 0.00365 day-1 for all deer. For the bucks, the slope of the long component was observed to decrease with age at time of spiking and to vary from a minimum for those spiked during antler dormancy to a maximum for those spiked during the antler growth period. There were no apparent effects of age and season on the kinetics of Sr in female deer. The model was developed to describe the uptake and retention of chronically ingested Sr. Due to the variations in the fractional intercept and slope of the long component, both associated with skeletal bone remodeling, the model utilized varying parameters. The predicted values were compared with those observed in a wild deer population and the close agreement added credibility to the coefficients of the total body retention equations utilized in the model