DAIRY CHEMISTRY AND BIOCHEMISTRY 0.16 0.14 0.12 0.04 0.02 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 a. an bv tation of total calcium is generally high both in early and late The concen station 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 strong244 DAIRY CHEMISTRY AND BIOCHEMISTRY 0.18 - 0.16- 0.14 - 0.12 - 0.1- a 6 & G 0.08- 0.06 - p ...d ...*.. , .o,. ... . .. * .... ....*O"' 9.. o"..*....* ,... * ... *... , , . , , .*. .... I.1.0 .I..*.. = = - ~ - 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