Bovine plasma alkaline phosphatase activity in relation to age, J substance and beta-lactoglobulin phenotypes.

Abstract

SummaryIn Jersey cattle the plasma alkaline phosphatase (AP) activity was found to be markedly age‐dependent. Among animals grouped with regard to age a marked decrease in the average plasma AP activity was shown to take place until an age of 21/2 to 3 years. For the J substance and β‐lactoglobulin phenotypes a dependency of age was not observed in the material studied.Excluding animals less than 3 years old and thus eliminating variation in AP activity due to age, a significant association (P<0.01) between AP activity and J phenotypes was observed among 91 animals. The Jcs phenotype was associated with low AP activity and the ja phenotype with high AP activity. On the average the J substance phenotypes, Jcs, Js and ja, exhibit an increasing plasma AP activity of 3.6, 4.2 and 6.8 King Armstrong Units, respectively, and a corresponding decrease in J substance.In a similar comparison of the β‐lactoglobulin phenotypes and plasma AP activity involving 82 lactating cows, an excess of the β‐lactoglobulin BB phenotypes with high AP activity just at P = 0.05 was observed.