Short communication: Influence of shortening the dry period of Swedish dairy cows on plasmin activity in milk.
The aim of this study was to evaluate the influence of shortening the dry period of Swedish dairy cows on plasmin activity and casein composition in milk. Swedish Holstein and Swedish Red cows, 45 in total, were assigned to a dry period of either 4 or 8wk. Milk samples were taken 10 and 5wk prepartum, and 6 and 12wk postpartum. Plasmin activity and plasminogen activity were measured with a spectrophotometric assay. Casein composition was measured by capillary zone electrophoresis. Prepartum plasminogen activity increased by 22% between 10 and 5wk prepartum, whereas no change in plasmin activity was observed during the same period. Cows with a 4-wk dry period had 61% higher plasmin activity in postpartum milk than cows with an 8-wk dry period. Cows of third or greater parity tended to have a stronger increase in plasmin activity as a result of applying a short dry period than cows of second parity. Although the αS1- and β-casein fractions declined with increasing plasmin activity, no dry period effects were found. Based on postpartum differences in plasmin activity, it was concluded that particularly multiparous cows require more than 4wk between lactations for recovery of the mammary epithelium. Changes in casein composition as an effect of plasmin activity are not expected to have a great effect on processing quality of milk, although future work is needed to verify this.
Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, PO Box 7024, 750 07 Uppsala, Sweden; Dairy Science and Technology, Food Quality and Design, Wageningen University, PO Box 8129, 6700 EV, Wageningen, the Netherlands. Electronic address: ruben2.devries@wur.nl.
Ruben
R
de Vries
Department of Food Science, Swedish University of Agricultural Sciences, PO Box 7051, 750 07 Uppsala, Sweden.
Melanie
M
Brandt
Department of Food Science, Swedish University of Agricultural Sciences, PO Box 7051, 750 07 Uppsala, Sweden.
Åse
Å
Lundh
Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, PO Box 7024, 750 07 Uppsala, Sweden.
Kjell
K
Holtenius
Dairy Science and Technology, Food Quality and Design, Wageningen University, PO Box 8129, 6700 EV, Wageningen, the Netherlands.
Kasper
K
Hettinga
Department of Food Science, Swedish University of Agricultural Sciences, PO Box 7051, 750 07 Uppsala, Sweden.
Monika
M
Johansson
D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary; D004734:Energy Metabolism; D005260:Female; D005341:Fibrinolysin; D007774:Lactation; D008892:Milk; D049590:Postpartum Period; D013548:Sweden
D005341:Fibrinolysin
casein composition; dairy cow; dry period; milk quality; plasmin activity