Metabolite levels and enzyme activities in the bovine mammary gland at different stages of lactation: I. Metabolite levels related to energy production

Abstract

SummarySamples of the mammary gland were obtained from heifers, lactating and dry cows by a freeze-clamping technique. Amounts of lactate, pyruvate, malate, ATP, ADP and AMP were determined in the sample extracts and calculated per g fresh weight and per mg DNA. Pyruvate, lactate and AMP amounts showed only minor changes at different stages of lactation, whereas quantities of malate, ATP and ADP were significantly higher in cows giving high milk yields. Pyruvate levels showed seasonal variations parallel to changes in milk composition. NAD: NADH ratios in mammary cytoplasm showed no significant differences between different groups of cattle, whereas ATP: AMP ratios in mammary gland samples were highest in lactating animals.