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

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Abstract
Comparisons were from tail and mam- mary-vein blood samples from 20 cows, both when the milk acetone test was posi- tive 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 arterio- venous differences (--.7 mg/100 ml) in acetoacetate plus acetone were consistently noted during subclinical ketosis, thus sug- gesting mammary ketogenesis. Within cow correlations between arteriovenous aceto- acetate plus acetone and arteriovenous non- esterified 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 triglyc- erides-fatty acids for milk fat synthesis. Within cow correlations between arterial levels and arteriovenous differences were .77"*, .82"*, and .83 *~ for glucose, non- esterified fatty acids, and triglycerides.