Serum Concentrations of the Milk Proteins -Lactalbumin and ß-Lactoglobulin in Pregnancy and Lactation: Correlations with Milk and Fat Yields in Dairy Cattle

¹ University of Wisconsin-Madison, Madison 53706

Serum concentrations of -lactalbumin and ß-lactoglobulin in first pregnancy, parturition, lactation, involution, and second parturition in 37 Holstein cattle were determined and used as an index of mammary status and in predicting milk yield. During first pregnancy, serum -lactalbumin increased in the last 3 mo and reached a peak at parturition (1100 ng/ml). Changes in -lactalbumin could not be described by a simple exponential equation, whereas changes in serum ß-lactoglobulin were described by a single exponential from second trimester until 4 wk prepartum and reached a peak at parturition (460 ng/ml). By 2 wk after parturition, -lactalbumin had dropped to approximately 140 ng/ml, and ß-lactoglobulin dropped to approximately 25 ng/ml. In late lactation, -lactalbumin was approximately 70 ng/ml and ß-lactoglobulin approximately 20 ng/ml. Short-term elevations were found after cessation of milking in both -lactalbumin and ß-lactoglobulin in serum. The concentrations of -lactalbumin and ß-lactoglobulin at second parturition were similar to those at first parturition with no differences found between parity. Both -lactalbumin and ß-lactoglobulin in serum were functionally associated with mammary growth and development. In heifers late in pregnancy, both serum concentrations of -lactalbumin and ß-lactoglobulin were positively correlated with mature equivalent milk and fat yields in the subsequent lactation. Serum ß-lactoglobulin concentrations at 16 wk prepartum in heifers were highly correlated with the sum of first and second lactation milk (r = .60) and fat (r = .60) yields. The potential value of using serum ß-lactoglobulin as an index for prescreening of heifers for lactation potential is discussed.

Key Words: milk yield • -lactalbumin • ßbeta;-lactoglobulin

Submitted on December 7, 1990
Accepted on April 15, 1991

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