Blood Metabolite Interrelationships and Changes in Mammary Gland Metabolism During Subclinical Ketosis

Abstract

Comparisons were from tail and mammary-vein blood samples from 20 cows, both when the milk acetone test was positive and after the test had become negative. The transition from subclinical ketosis to normal was marked by increasing glucose and triglycerides and decreasing acetate, ketone bodies, and nonesterified fatty acids. Also noted were increasing arteriovenous differences in glucose and triglycerides and a decreasing arteriovenous difference in nonesterificd fatty acids. Negative arteriovenous differences (--.7 mg/100 ml) in acetoacetate plus acetone were consistently noted during subclinical ketosis, thus suggesting mammary ketogenesis. Within cow correlations between arteriovenous acetoacetate plus acetone and arteriovenous nonesterified fatty acids (--.69**) indicated that conditions favoring increased uptake of nonesterified fatty acids also favored increased mammary ketogenesis. A similar type of correlation between arteriovenous nonesterified fatty acids and arteriovenous triglycerides (--.58 *) indicated a possible substitution of nonesterified for triglycerides-fatty acids for milk fat synthesis. Within cow correlations between arterial levels and arteriovenous differences were .77"*, .82"*, and .83 *~ for glucose, nonesterified fatty acids, and triglycerides.