title: Changes in protein and nutrient composition of milk throughout lactation in dogs.
abstract: OBJECTIVE
  To evaluate changes in protein and nutrient composition of milk throughout lactation in dogs.
  
  
  METHODS
  Milk samples collected from 10 lactating Beagles.
  
  
  METHODS
  Milk samples were collected on days 1, 3, 7, 14, 21, 28, 35, and 42 after parturition and analyzed to determine concentrations of nitrogen, nonprotein nitrogen, casein, whey proteins, amino acids, lipids, lactose, citrate, minerals, and trace elements. Optimum conditions for separating casein from whey proteins and distribution of milk proteins throughout lactation were assessed by use of polyacrylamide gel electrophoresis.
  
  
  RESULTS
  Protein concentration was high in samples collected on day 1 (143 g/L), decreased through day 21 (68.4 g/L), and increased thereafter. Concentration of nonprotein nitrogen did not change throughout lactation (5.7 to 9.9% of total nitrogen content). Casein-to-whey ratio was approximately 70:30 and remained constant throughout lactation. Lactose concentration increased from 16.6 g/L on day 1 to 34.0 to 40.2 g/L on days 7 to 42. Lipid concentration ranged from 112.5 to 1372 g/L. Citrate concentration increased from day 1 (4.8 mM) to day 7 (6.6 mM), then gradually decreased until day 42 (3.9 mM). Iron, zinc, copper, and magnesium concentrations decreased during lactation, whereas calcium and phosphorus concentrations increased. Calcium-to-phosphorus ratio remained constant throughout lactation (approx 1.6:1). Energy content of milk ranged from 1,444 to 1,831 kcal/L.
  
  
  CONCLUSIONS
  Protein and nutrient composition of milk changes throughout lactation in dogs. These data can provide valuable information for use in establishing nutrient requirements of puppies during the suckling period.
authors.affiliation: Department of Nutrition, College of Agricultural and Environmental Sciences, University of California, Davis 95616, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Adkins
authors.forename: A J
authors.initials: AJ
authors.lastname: Lepine
authors.forename: B
authors.initials: B
authors.lastname: Lönnerdal
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002364:Caseins / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism; D004285:Dogs / Q000378:metabolism / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D005260:Female; D007774:Lactation / Q000502:physiology*; D007785:Lactose / Q000378:metabolism; D050356:Lipid Metabolism; D008137:Longitudinal Studies; D008892:Milk / Q000378:metabolism*; D008894:Milk Proteins / Q000378:metabolism*; D008903:Minerals / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D000067816:Whey Proteins
chemical_list: D000596:Amino Acids; D002364:Caseins; D008894:Milk Proteins; D008903:Minerals; D000067816:Whey Proteins; D019343:Citric Acid; D007785:Lactose; D009584:Nitrogen