AbstractFive milliliters of Slanetz No. 7 Staphylococcal Toxoid were injected intramuscularly into 43 pregnant heifers in 3 herds; a booster dose was given 1 month later. The antibody level in both the blood sera and the milk wheys of these heifers was determined through a 13-month period. The average blood-serum titer reached a 1:50 level 1 month after vaccination, and remained around that level until the fifth postvaccinal month. Thereafter, a continuous and rapid decrease in titer was observed until the 11th postvaccinal month. An increase in titer was observed after the annual booster dose was given. Although the staphylococcal antibody titers in milk wheys from two herds showed a peak in the third month, the levels went steeply down at the 5th-month observation. The general average trend was a steady and steep decrease in milk-whey antibody titer through the 11-month postvaccinal observation period, with a very feeble response after the annual booster dose.
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