Mammary involution in ewes: Changes in milk plasminogen and plasmin
D.D.S. Mackenzie, Y.H. Cottam, R.J. Knutson, S.N. McCutcheon
Department of Animal Science, Massey University, Palmerston North,
New Zealand.
Proceedings of the New Zealand Society of Animal Production 1994,
54: 107-110
Multiparous Border Leicester x Romney ewes were weaned early (day 35
of lactation), milked to empty the mammary gland and again milked 18 h later
(day 0 of experiment) to establish baseline milk yields and concentrations in
milk of the proteolytic enzyme plasmin and its zymogen plasminogen. They
were then divided into 3 groups to be milked 3 (n=5), 8 (n=6) or 15 (n=5) days
after the day 0 milking to determine changes in concentrations and yields of
plasmin and plasminogen in mammary gland secretions during involution.
Yields (mean±SE) on days 0 (groups 1 + 2 + 3), 3 (group 1), 8 (group 2) and 15
(group 3) were: secretion (g), 785±31.2 v. 598±94.8 v. 478±86.8 v. 51±66.6;
plasminogen (mg), 7.8±2.2 v. 78.7±11.1 v. 22.4±4.6 v. 3.9±2.1; and plasmin
(ug), 11.5±2.38 v. 148.5±8.00 v. 51.6±7.92 v. 4.9±2.32. Corresponding
concentrations in the secretions were (ug/ml): plasminogen, 0.01±0.002 v.
0.15±0.027 v. 0.046±0.005 v. 0.061±0.007; and plasmin, 0.015±0.006 v.
0.275±0.027 v. 0.118±0.011 v. 0.083±0.009. There was a linear decline in the
volume of secretions from day 0 to day 15. In contrast there was a transient
increase (15 fold) in plasminogen and plasmin yields by 3 days after milking.
These data suggest that any role of plasmin in mammary gland involution is
likely to be limited to the first week after early weaning.
Keywords: NZSAPAB;
Early weaning; milk; plasmin; plasminogen; involution.
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Last Updated 25-01-1997
