title: Physical properties of mammary secretions in relation to chemical changes during transition from colostrum to milk.
abstract: We examined the physical and chemical changes in milk during early lactation, and how these changes were affected by leaving one quarter unmilked in either the first or second milking, with the purpose of discriminating between colostrum and normal milk. Milk samples were collected from each quarter of 17 cows during the first 5 d after calving and then after about 7 d and 14d. Samples were analysed for somatic cell count (SCC), fat, protein, casein, lactose, IgG1, colour, plasmin, pH and coagulation properties. Large variations occurred in both chemical and physical properties throughout the study period. Within six milkings, the concentration of casein decreased by 60%, IgG1 by 94%, and lactose increased by 34%. At milking number 6, rennet coagulation time was lowest and curd firmness was highest. The pH increased from 6.4 to 6.7 over the period of the experiment, and the colour changed from yellow (reddish) to white. Coagulation properties and the pH fell within the range of normal milk after five milkings. Measurement of colour and density appeared to be a potential method for detection of milk unsuitable for the dairy factory. Effects of omitting one quarter in one milking differed between milk components, but seemed to be of little importance to the physical properties.
authors.affiliation: Department of Animal Health and Welfare, Danish Institute of Agricultural Sciences, Blichers Allé, DK-8830 Tjele, Denmark.
authors.forename: Birgitte D
authors.initials: BD
authors.lastname: Madsen
authors.forename: Morten D
authors.initials: MD
authors.lastname: Rasmussen
authors.forename: Mette O
authors.initials: MO
authors.lastname: Nielsen
authors.forename: Lars
authors.initials: L
authors.lastname: Wiking
authors.forename: Lotte B
authors.initials: LB
authors.lastname: Larsen
mesh_terms: D000818:Animals; D002364:Caseins / Q000032:analysis; D002417:Cattle; D002452:Cell Count; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003116:Color; D003126:Colostrum / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005341:Fibrinolysin / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000032:analysis; D007774:Lactation; D007785:Lactose / Q000032:analysis; D008055:Lipids / Q000032:analysis; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008892:Milk / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*; D008894:Milk Proteins / Q000032:analysis; D013997:Time Factors
chemical_list: D002364:Caseins; D007074:Immunoglobulin G; D008055:Lipids; D008894:Milk Proteins; D005341:Fibrinolysin; D007785:Lactose