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SIGNIFICANCE OF THE CHEMICAL COMPOSITION OF THE SECRETING AND DRY MAMMARY GLAND TO MILK SECRETION
1Department of Animal Pathology of The Rockefeller Institute for Medical Research, Princeton, N. J., and the Maine Agricultural Experiment Station, Orono.
The Journal of General Physiology
|October 30, 2009
Summary
Dairy cows retain approximately 2.1 pounds of milk in the udder when believed dry, containing lactose synthesized from blood dextrose as needed for milk production.
Area of Science:
- Dairy Science
- Animal Physiology
- Biochemistry
Background:
- Milk secretion is a complex physiological process in mammals.
- Understanding the composition of residual milk in the udder is crucial for dairy management.
Purpose of the Study:
- To investigate the composition of milk retained in the udder of dairy cows post-milking.
- To determine the stage of lactose synthesis in relation to milk secretion.
Main Methods:
- Analysis of udder composition (fat, ash, nitrogen, lactose) in lactating cows.
- Quantification of lactose in milk and residual udder content.
- Comparison of 'dry' udder composition with actively secreting gland.
Main Results:
- Cows retain the lactose equivalent of up to 30 pounds of milk in the udder.
- An average of 2.1 pounds of residual milk, rich in lactose, is found in the 'dry' udder.
- The dry udder shows excess fat, ash, and nitrogen compared to milk, with reduced sugar and ash content.
Conclusions:
- Lactose appears to be synthesized from blood dextrose only as needed for milk formation.
- The composition of the dry udder differs significantly from the actively secreting gland, indicating a distinct physiological state.
- This study identifies an additional stage in milk secretion related to residual milk composition.
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