INFLUÊNCIA DA FASE DE LACTAÇÃO NAS PROTEÍNAS DO SORO LÁCTEO DE

INFLUENCE OF LACTATION PHASE ON WHEY PROTEINS OF JERSEY COWS To assess the influence of lactation phase on whey proteins, we collected 48 milk samples from 12 Jersey cows before milking. They were divided into three groups: early lactation (70 to 120 days); middle of lactation (121 to 202 days); and end of lactation (214 to 358 days). The whey was obtained by milk coagulation with renin. Furthermore, serum proteinogram was determined by biuret method and protein digest was fractionated by polyacrymalide gel electrophoresis (SDS-PAGE). There was a gradual and significant decrease in whey components during the lactation period, such as serum albumin, lactoferrin, immunoglobulins, beta-lactoglobulin, and alpha-lactalbumin. We recommend the following mean values for whey proteins of Jersey cows: Total whey protein = 640 mg/dL; Lactoferrin= 40 mg/dL; Albumin = 30 mg/dL; Immunoglobulin heavy chain = 40 mg/dL; Immunoglobulin light chain = 80 mg/dL; Beta-lactoglobulin = 230 mg/dL; Alpha-lactalbumin = 140 mg/dL.