Factors Affecting Herd Milk Composition and Milk Plasmin at Four Levels of Somatic Cell Counts

A longitudinal study was carried out on samples of bulk tank milk collected from 200 farms for 12 mo to evaluate SCC, plasmin and plasminogen activities, psychrotrophic bacteria count, and protein quality in milk and to examine the proteolytic effects of plasmin on milk proteins. Herds were selected...

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Bibliographic Details
Published in:Journal of dairy science 1995-10, Vol.78 (10), p.2186-2195
Main Authors: Ballou, Linda U., Pasquini, Marina, Bremel, Robert D., Everson, Thomas, Sommer, Dean
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Caseins - metabolism
Cattle
Cell Count
Cheese
Female
Fibrinolysin - metabolism
Food industries
Fundamental and applied biological sciences. Psychology
Lactose - metabolism
Lipid Metabolism
Milk - chemistry
Milk - cytology
Milk - metabolism
Milk and cheese industries. Ice creams
milk composition
Milk Proteins - metabolism
Multivariate Analysis
plasmin
Plasminogen - metabolism
psychrotrophs
somatic cells
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Summary:A longitudinal study was carried out on samples of bulk tank milk collected from 200 farms for 12 mo to evaluate SCC, plasmin and plasminogen activities, psychrotrophic bacteria count, and protein quality in milk and to examine the proteolytic effects of plasmin on milk proteins. Herds were selected randomly from client lists of two dairies to create four groups based on milk SCC of the month before the study; herds were reassigned monthly to one of four groups based on SCC for that month. Overall means were 3.73% fat, 3.13% protein by infrared analysis, 3.16% protein by Kjeldahl analysis, 2.42% casein percentage, 4.65% lactose, 5.43 cells/ml of log SCC, 1.13 U of plasmin, 45.6 U of plasminogen, and log 2.86 cfu/ml of psychrotrophic bacteria. The ANOVA showed a significant effect of month on all factors except SCC, which was fixed by the experimental design. Plasmin and plasminogen activities were high from December to May. Plasmin activities and psychrotroph counts were significantly higher for the high SCC group. Casein percentage and number were significantly higher for the low SCC group.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(95)76846-1