Influence of Grazing Intensity on Cesium-137 Levels in Milk

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Abstract
The influence of grazing intensity on radiocesium concentrations in cows'' milk was studied by the accepted rotational grazing system of the Department of Dairy Industry, Utah State University. Three comparable groups of Holstein cows were chosen. The 1st group was included in the main herd, the 2nd group followed the main herd in the same rotation but always a plot behind, and the third group had no access to pasture. A difference (P < 0.1) based on per cent deviation was found in Csl37 levels in the milk of the first and second groups. For further statistical analysis, the data for the 1st and 2nd groups were classified into 2 periods, based on whether precipitation occurred during sample collection. No significant difference (P > 0.1) was evident during the rainy period, but a significant difference (P < 0.001) was observed for the dry interval. The correlation coefficient for the same periods was significant (P < 0.0001) and positive. For both groups a significant positive correlation (P < 0.0001) was also obtained for Sr90 versus Csl37 concentration in milk. The 3rd group, consuming only hay and grain, excreted 9 to 10% of its total intake of Csl37 into the milk.

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