title: Effect of cow-specific factors and feeding frequency of concentrate on diurnal variations of blood metabolites in dairy cows.
abstract: OBJECTIVE
  To determine the effect of feeding frequency and cow-specific factors on diurnal variations of blood metabolites concentrations.
  
  
  METHODS
  40 dairy cows from 2 herds.
  
  
  METHODS
  Each herd was fed concentrate at a specific feeding frequency (automatic vs twice daily). Blood samples were collected 4 times daily. Plasma concentrations of glucose, nonesterified fatty acids (NEFA), and beta-hydroxybutyrate (BHBA) were analyzed, and concentrations of urea, cholesterol, and total protein (TP) were determined in serum samples. A multivariate repeated-measures ANOVA was used to test the effect of time, feeding frequency, production group, parity, days after parturition, and daily milk yield on diurnal variations of metabolites.
  
  
  RESULTS
  Concentrations of glucose, BHBA, and urea remained relatively constant in the herd that was fed by use of automatic distribution of concentrate; however, significant diurnal patterns were detected in the herd fed only twice daily. Only slight differences in glucose and urea concentrations were detected between high- and low-producing cows, but concentration of BHBA was significantly influenced by number of days in lactation. In contrast, diurnal variations in NEFA and cholesterol concentrations were similar between the 2 herds but differed with regard to production group. Concentrations of TP did not have relevant diurnal patterns and did not differ between production groups.
  
  
  CONCLUSIONS
  Diurnal variations and feeding frequency affect glucose, BHBA, and urea concentrations in cows. In contrast, concentrations of NEFA, cholesterol, and TP appear to be less sensitive to time of sample collection. Feeding frequency, composition of feed, or both, have a major impact on blood metabolites concentrations.
authors.affiliation: Department of Clinical Sciences, University of Montreal, St-Hyacinthe, QC, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Eicher
authors.forename: A
authors.initials: A
authors.lastname: Liesegang
authors.forename: E
authors.initials: E
authors.lastname: Bouchard
authors.forename: A
authors.initials: A
authors.lastname: Tremblay
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001798:Blood Proteins / Q000032:analysis; D002417:Cattle / Q000097:blood*; D002784:Cholesterol / Q000097:blood; D002940:Circadian Rhythm; D003612:Dairying; D004435:Eating; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female
chemical_list: D001786:Blood Glucose; D001798:Blood Proteins; D005230:Fatty Acids, Nonesterified; D002784:Cholesterol; D020155:3-Hydroxybutyric Acid