Lactation Stage, Parity, and Infection Affecting Somatic Cells, Electrical Conductivity, and Serum Albumin in Milk

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Abstract
Effects of stage of lactation and parity on cell concentration, electrical conductivity and serum albumin concentration of milk from quarters of known infection status were examined in dairy cows. In quarters free from infection, somatic cell concentration rose from 80 to 160 .times. 103 cells/ml between 35-285 days postpartum; in quarters infected with Staphylococcus aureus, the increase was from 250 to .apprx. 100 .times. 103 cells/ml. As lactation number advanced, there was little change in cell concentration for quarters free from infection; in quarters infected with S. aureus, cell concentration rose from .apprx. 450 .times. 103 cells/ml for 1st lactation to .apprx. 1500 .times. 103 cells/ml for cows in their 6th or more lactations. Trends in electrical conductivity were similar to those for cell concentration, with the main influence on electrical conductivity being S. aureus infection. For serum albumin concentration, only the effect of stage of lactation was significant. Concentration of serum albumin rose from 150 mg/l at the beginning of lactation to 280 mg/l at 215 days postpartum. Effects of stage and number of lactation were minor compared with effects of infection by S. aureus.