Effect of energy metabolism on 13C/12C-ratios in milk fat and lactose of cows.
1. The ratios of stable carbon isotopes 13C/12C in milk constituents of Holstein dairy cattle were investigated by mass spectrometry. 2. Under physiological feeding conditions the natural abundance of 13C in lactose was greater than in milk fat. 3. Reduction of energy intake diminished the abundance of 13C in lactose resulting in values similar to those of fat. 4. It is suggested that by comparing the 13C/12C ratios in milk fat and lactose the metabolic energy state of cows may be rated.
Schulze
E
E
Fachgebiet für Medizinische Physik, Tierärztlichen Hochschule Hannover Bischofsholer Damm 15, Germany.
Diop
H
H
Breves
G
G
Giese
W
W
D000818:Animals; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes; D002417:Cattle / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005508:Food Deprivation / Q000502:physiology; D007785:Lactose / Q000378:metabolism*; D050356:Lipid Metabolism; D008892:Milk / Q000378:metabolism*
D002247:Carbon Isotopes; D002244:Carbon; D007785:Lactose