Rhythms in Cholesterol, Cholesteryl Esters, Free Fatty Acids, and Triglycerides in Blood of Lactating Dairy Cows

• Published in: Journal of dairy science Vol. 73; no. 4; pp. 948 - 955
• Main Authors: Bitman, Joel, Wood, D.L., Lefcourt, A.M.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.04.1990; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: ACIDE GRAS LIBRE; ACIDOS GRASOS LIBRES; Animals; Biological and medical sciences; BIOLOGICAL RHYTHMS; BLOOD; Blood Urea Nitrogen; BOVIN LAITIER; Cattle - blood; CHOLESTEROL; Cholesterol - blood; Cholesterol Esters - blood; Chromatography, Thin Layer; Circadian Rhythm; COLESTEROL; COWS; DAIRY CATTLE; Eating; ESTER; ESTERES; ESTERS; Fatty Acids, Nonesterified - blood; Female; Food industries; FREE FATTY ACIDS; Fundamental and applied biological sciences. Psychology; GANADO DE LECHE; Hydrocortisone - blood; LACTACION; LACTATION; Lactation - blood; LIPIDE; LIPIDOS; LIPIDS; Lipids - blood; Milk and cheese industries. Ice creams; plasma lipids; rhythms; RITMOS BIOLOGICOS; RYTHME BIOLOGIQUE; SANG; SANGRE; TRIGLICERIDOS; TRIGLYCERIDE; TRIGLYCERIDES; Triglycerides - blood; Triiodothyronine - blood; VACA; VACHE; rhythms; plasma lipids; cows; Vertebrata; Mammalia; Chronobiology; Ox; Lipids; Serum; Chemical composition; Cow; Artiodactyla; Ungulata
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(90)78751-6

Blood samples from six lactating dairy cows were analyzed to determine whether circulating neutral lipids exhibit rhythmic variations. Plasma neutral lipids were measured by quantitative TLC on every fourth integrated 15-min blood sample taken over 48-h periods. Cows were housed in an environmental chamber at 20°C with 16h light:8h dark (lights on at 0700h), fed daily at 0900h, and milked at 0830 and 2000h. Other variables monitored included: body temperature, ammonia nitrogen, urea nitrogen, glucose, triiodothyronine, thyroxine, somatotropin, insulin, cortisol, and prolactin. Mean concentrations of cholesterol, cholesteryl esters, free fatty acids, and triglycerides were 21.4, 175.4, 3.1, and 6.3 mg/dl, respectively. Visual and power spectral analysis of the pulsatile fluctuations in lipids indicated rhythms with periods of 2 to 3h. Amplitudes of rhythms for free fatty acids and triglycerides were 60% of mean concentrations and for cholesterol and cholesteryl esters were 20% of mean concentrations. The presence of these rhythms was conserved when data were averaged across time by cow. However, because of nonstationary conditions, rhythms identified by spectral analysis were not statistically significant. There was no evidence of circadian patterns in circulating neutral lipid components. All other metabolic and hormonal variables except cortisol exhibited distinct circadian rhythms.