Dairy Chemistry And Biochemistry

244 DAIRY CHEMISTRY AND BIOCHEMISTRY

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Weeks of lactation

Figure 5.2 Changes in the concentrations of calcium (----) and phosphorus (-) in bovine milk
during lactation.

5.5.2 Stage of lactation

The concentration of total calcium is generally high both in early and late
lactation but in the intervening period no relation with stage of lactation is
evident (Figure 5.2). Phosphorus shows a general tendency to increase as
lactation advances (Figure 5.2). The concentrations of colloidal calcium and
inorganic phosphorus are at a minimum in early and at a maximum in late
lactation milk. The concentrations of sodium and chloride (Figure 5.3) are
high at the beginning of lactation, followed by a rapid decrease, then
increase gradually until near the end of lactation when rapid increases occur.
The concentration of potassium decreases gradually throughout lactation.
The concentration of citrate, which has a marked influence on the distribu-
tion of calcium, shows a strong seasonal variation (Figure 5.4), influenced
more by feed than the stage of lactation. The pH of milk shows a strong