Milk analysis experiment
reveals nutrient changes
THE Department of Nutrition, College of Agricultural and Environmental Sciences, University of California, Davis 95616, USA in 2001 conducted an experiment to gauge the changes in the protein and nutrient composition of milk throughout lactation in dogs.The experiment was conducted by Y Adkins, AJ Lepine and B Lönnerdal.
Milk samples were collected from 10 lactating Beagles. The samples were collected on days 1, 3, 7, 14, 21, 28, 35, and 42 after birth of the puppies and was analyzed to determine the concentrations of nitrogen, non-protein 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. The findings were that the 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 non-protein nitrogen did not change throughout lactation (5.7 to 9.9percent 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. The calcium-to-phosphorus ratio remained constant throughout lactation (approx 1.6:1). The energy content of milk ranged from 1,444 to 1,831 kcal/L.
The experiment concluded that the protein and nutrient composition of milk changes throughout lactation in dogs. This data provided valuable information for use in establishing the nutrient requirements of puppies during the suckling period.
(The above experiment is interesting and informative, especially for breeders, but is also valuable to show breeders and puppy buyers that puppies should not be weaned before they are ready, and who better to judge when they are ready than their mother! The ideal time averages out at around 10 weeks. Many breeders take puppies away from their mother too early, some as young as four weeks, and these puppies not only lose the valuable teaching and comfort of their mother but also the perfectly calibrated nutrition that she provides for them - Ed)
