Effects of stage of lactation and time of year on plasmin-derived proteolytic activity in bovine milk in New Zealand

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dc.contributor.authorNicholas, Gina D.
dc.contributor.authorAuldist, Martin J.
dc.contributor.authorMolan, Peter C.
dc.contributor.authorStelwagen, Kerst
dc.contributor.authorProsser, Colin G.
dc.coverage.spatialEnglanden_NZ
dc.date.accessioned2008-08-18T02:57:54Z
dc.date.available2008-08-18T02:57:54Z
dc.date.issued2002
dc.description.abstractThe objective of this study was to determine the effects of stage of lactation (SOL) and time of year on plasmin-derived proteolytic activity in the milk of pasture-fed dairy cows in New Zealand. Four herds of 20 Friesian cows were used, one herd calving in each of January, April, July and October. Cows grazed ryegrass/white clover pasture only, except during June (winter) when all cows received supplementary pasture silage. Milk samples were collected on four occasions during the year (spring, summer, autumn and winter) from each cow in milk, to give a total of three samples per cow (early, mid and late lactation; c. 30, 120 and 220 days after calving, respectively). Milk samples were analysed for plasmin-derived proteolytic activity. There was no effect of either SOL or time of year on plasmin activity and therefore yields of plasmin followed patterns in milk yield (highest in early lactation and in summer). There were effects of both SOL and time of year on plasminogen-derived and total plasmin plus plasminogen-derived activity, both of which were highest in late lactation and in spring. Changes in plasminogen-derived activity and total plasmin plus plasminogen-derived activity due to SOL were not only due to the decrease in milk yield associated with advancing lactation, because enzyme yields were also increased with advancing lactation. Similarly, effects of time of year on plasminogen-derived activity and total plasmin plus plasminogen-derived activity could not be attributed solely to concomitant changes in milk yield, and may be influenced by the variation in the quality and quantity of feed during the year inherent in a pasture-based dairy system. Effects of SOL on proteolytic activity were greater than, and independent of, effects of time of year.en_US
dc.format.mimetypeapplication/pdf
dc.identifier.citationNicholas, G. D., Auldist, M. J., Molan, P. C., Stelwagen, K., & Prosser, C. G. (2002). Effects of stage of lactation and time of year on plasmin-derived proteolytic activity in bovine milk in New Zealand. Journal of Dairy Research, 69(04), 533-540.en_US
dc.identifier.doi10.1017/S0022029902005745en_US
dc.identifier.issn0022-0299
dc.identifier.urihttps://hdl.handle.net/10289/956
dc.language.isoen
dc.publisherCambridge University Pressen_NZ
dc.relation.isPartOfJournal of Dairy Researchen_NZ
dc.relation.urihttp://journals.cambridge.org/action/displayJournal?jid=DARen_US
dc.rightsThis article is published in the Journal of Dairy Research. Copyright © Proprietors of Journal of Dairy Research 2002.en_US
dc.subjectmilk proteinen_US
dc.subjectplasminen_US
dc.subjectproreolysisen_US
dc.subjectlactationen_US
dc.subjectseasonalityen_US
dc.titleEffects of stage of lactation and time of year on plasmin-derived proteolytic activity in bovine milk in New Zealanden_US
dc.typeJournal Articleen_US
pubs.begin-page533en_NZ
pubs.elements-id27850
pubs.end-page540en_NZ
pubs.issue4en_NZ
pubs.volume69en_NZ
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