Development of a dynamic prediction model for radio-cesium concentration of beef and excretion in beef cattle production systems in Japan

Abstract

A dynamic simulation model for prediction on the transfer of radio-cesium, released after Fukushima accident, from feed into beef was developed. The model simulated radio-cesium concentrations in beef (muscle plus fat in carcass) and radio-cesium excretions with feces and urine from birth to slaughter. The model was used to examine the effects of radio-cesium contaminated situations in the calf period and various levels of radio-cesium concentrations in roughage during the feedlot period on radio-cesium concentration in beef and whole life excretion. The base situation was that average daily gain was 0.7 kg/day and slaughter weight was 700 kg. The two cases of transfer coefficients (the average value of 0.0385 and the upper value of 0.096) were assumed and the effect of a different management option (increased average daily gain during the feedlot period and smaller slaughter weight) was also investigated. The result showed that the predicted radio-cesium concentrations in beef at slaughter be below the maximum permitted level of radio-cesium concentration in beef (500 Bq/kg) under the regulation for radio-cesium content in feed by the Japanese government (5000 Bq/kg for a calf and 300 Bq/kg for a feedlot seer). The effect of contamination situation in the calf period on the concentration in beef at slaughter was negligible because of long feedlot period in Japan. It was however suggested that the case in extremely high radio-cesium concentration in roughage (more than 5000 Bq/kg) under the upper transfer coefficient may be above permitted level. Further, total radio-cesium excretion in whole life was remarkably large even under regulation level, indicating that considerable attention should be given when the excretion would be used as manure for crop production and fertilizer for gardening.