title: Cow's milk quality and energy value during different lactation stages.
abstract: BACKGROUND
  The quality of dairy products, raw milk in particular, depends on many factors. Low bacterial and somatic cell counts are basic determinants of the appropriate raw milk quality. The objective of the work was to assess the effect of selected factors, that is, the age of cows and their daily milk performance, on cytological quality (somatic cell count) and energy value of milk produced at individual stages of lactation.
  
  
  METHODS
  Somatic cell count and energy value of cow's milk were assessed. A total of 229 792 milk samples were examined. Data for analysis were taken from milk records of 350 dairy herds.
  
  
  RESULTS
  It was demonstrated that, of all the lactations studied, the fi rst lactation (from calving to the 100th day of lactation) was characterised by the highest daily milk performance (25.1 kg) and the lowest somatic cell count (356 thous./1 ml), fat, protein and dry matter contents (4.06, 2.96 and 12.41%, respectively) and milk calorific value (732 kcal/kg). The highest energy value was recorded in cow's milk produced towards the end of lactation, that is from day 300 till the end of lactation (842 kcal/kg).
  
  
  CONCLUSIONS
  High milk calorific value in late lactation and high fat and protein contents were accompanied by low raw milk quality.
authors.affiliation: Department of Cattle Breeding and Milk Evaluation, Siedlce University of Natural Sciences and Humanities, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Salamończyk
mesh_terms: D000367:Age Factors; D000818:Animals; D002452:Cell Count; D004041:Dietary Fats / Q000032:analysis; D005260:Female; D006822:Hybrid Cells / Q000166:cytology; D007774:Lactation / Q000502:physiology*; D007785:Lactose / Q000032:analysis; D008892:Milk / Q000737:chemistry* / Q000166:cytology; D008894:Milk Proteins / Q000032:analysis; D009753:Nutritive Value; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D008894:Milk Proteins; D007785:Lactose