Influence of level of feeding and stage of lactation on proteolytic
activity in bovine milk
G.D. Nicholas, C.G. Prosser, K. Stelwagen and T.R. Mackle
Dairy Science Group, AgResearch, Ruakura Research Centre, Private
Bag 3123, Hamilton, New Zealand.
Proceedings of the New Zealand Society of Animal Production, 1996,
56: 114-117
Using a Latin square cross-over design, twelve sets of identical
Friesian or Friesian x Jersey twin cows during spring (early lactation: 42 ± 3
d in milk), were assigned to both a high (5 kg DM/d of a barley-based
concentrate in addition to ad lib. pasture), or low (restricted to 70% of their
metabolic energy requirements) level of feeding, separated by periods of
uniformity (ad lib. access to pasture). The trial was repeated in summer
(mid lactation: 177 ± 3 d in milk). During spring, low feed reduced milk
yield by up to 30%, and during summer, high feed increased milk yield by
up to 26%. Proteolytic activity (plasmin + plasminogen-derived activity)
was not significantly altered by high feed during either stage of lactation,
however during spring, low feed increased activity by up to 33%. The
significant interaction between level of nutrition and stage of lactation
should be considered when planning management strategies to maximise
milk quantity and quality.
Keywords: NZSAPAB;
Plasmin; plasminogen; stage of lactation; nutrition; cows; milk.
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Last Updated 18-03-1997
