Strontium and Calcium Uptake and Excretion in Lactating Dairy Cows

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Abstract
Sr89 and Ca45 were given orally in single doses to lactating dairy cows. During a 9 days experimental period, the average amounts of administered Sr89 found in milk and urine of 8 cows were 0.55 [plus or minus]0.05 and 1.8 [plus or minus] 0.30% respectively. Under the same conditions for 4 cows, averages of 3.77 [plus or minus] 0.17 and 0.82 [plus or minus] 0.08% of the administered Ca45 were found in milk and urine, respectively. The average observed ratios of Sr89/Ca45 for 4 cows were: blood-diet = 0.33; urine-diet = 1.82; milk-diet = 0.15; milk-blood = 0.44; urine-blood = 5.43. The excretion patterns for Sr89 in milk, urine, and feces can be described almost entirely by exponential functions of time.