Serum lipids and apolipoprotein (apo) B and A-I concentrations were determined in 164 dairy cows which had undergone liver biopsy in early lactation. The animals were divided into groups according to fatty liver severity on the basis of hepatic triglyceride content. The serum free fatty acid (FFA) concentration was higher in cows that developed fatty livers than in normal cows, and it correlated highly with liver triglycerides. Serum total cholesterol and triglyceride levels did not correlate with hepatic triglycerides. Both apo B and apo A-I levels were significantly decreased in fatty liver cows. In particular, apo B levels showed a strongly negative correlation with liver triglycerides. The present results suggest that hepatic apolipoprotein synthesis is impeded in fatty liver cows.

Zusammenfassung In verschiedenen physiologischen Stadien bei der Milchkuh wurden FFS, Triglyceride, Gesamtcholesterin und Apolipoprotein B und A‐I im Serum sowie die Triglyceride in der Leber bestimmt. Im Serum der Milchkühe wurden generell niedrige Triglycerid‐ und Apolipoprotein B‐ und hohe Cholesterin‐ und Apolipoprotein A‐I‐Werte gemessen. Die niedrigsten Werte für Serum‐Triglyceride und die höchsten für Cholesterin wurden in der Mitte der Laktation bestimmt. Die Apolipoprotein A‐I‐Konzentration lag in der Trockenzeit am niedrigsten und stieg während der Laktation progressiv an. Das Einsetzen der Laktation war begleitet von den höchsten Konzentrationen an FFS im Serum und Triglyceriden in der Leber. Zur gleichen Zeit wurden die niedrigsten Werte für Triglyceride, Gesamtcholesterin und Apolipoprotein B im Serum der Milchkühe gefunden. Die Ergebnisse werden im Zusammenhang mit dem Energiebedarf während Trächtigkeit und Laktation diskutiert und mil anderen Tierspecies verglichen.

The relationships between fatty liver in dairy cows and reduced levels of plasma lipoproteins, and particularly of low density lipoproteins (LDL), has been previously described. Since electrophoretic heterogeneity of ultracentrifugally isolated LDL (d, 1.006–1.063 g/ml) has been found, the exact nature of this reduction in cows with fatty liver was investigated. Lipoproteins from control and severely afflicted animals were isolated by ultracentrifugation and affinity chromatography on heparin‐Sepharose CL 6 B. Gradient gel electrophoresis of lipoproteins on 4–30% gels and an immunolocalization study of apoprotein A‐I (apo A‐I) showed that control animals have two subpopulations of apo A‐I‐containing particles with a mean radius of 6.52 and 5.05 nm. In the fatty liver cows, the former was clearly shifted toward smaller particles. We concluded that the depressed level and compositional modifications of LDL in severe fatty liver cows result from a decrease in the oversized apo A‐I‐containing lipoproteins which can be isolated in the LDL density range. This could stem from the decreased supply of triglyceride‐rich lipoprotein surface components for the production of these lipoproteins. The modifications can be plausibly explained by a reduced synthesis or secretion of very low density lipoproteins (VLDL) by the liver.

No abstract

Plasma lipid, apolipoprotein (apo) B and apo A-I concentrations were measured in fetal calves in the age range of 4–9 months. The results were compared with those obtained from preruminant calves and cows. The studied lipids and apolipoproteins underwent quantitative changes during development. Fetal calves, as compared to preruminant calves and cows, had a particularly low apo A-I concentration and a high apo B/apo A-I ratio. Unlike adult animals which have two forms of apo B, fetal calves had only high molecular weight apo B (apo Bh). During fetal development triglyceride, cholesterol and apo B concentrations decreased, but apo A-I concentrations remained constant.