Diurnal variation in concentration of Beta-lactoglobulin in bovine
milk.
R.D. McLaren, M.J. Auldist and C.G. Prosser.
AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton
Proceedings of the New Zealand Society of Animal Production. 1998,
58: 49-51
Two trials were conducted to define the variation in
concentrations of Beta-lactoglobulin (Beta-LG) in bovine milk following
different milking intervals. In the first, milk samples were collected
from three herds of 20 cows. At the time of sampling in early summer,
one herd was in each of early, mid and late lactation (30, 120 and 210
days post calving, respectively). Average Beta-LG concentrations were 41,
37 and 50% higher (p<0.05) after a 16h than 8h milking interval for
early, mid and late lactation, respectively. In the second trial, bulk
milk was sampled from four herds of 12 cows. All cows were at the same
stage of lactation and the milking interval was 16:8h. Samples were
collected on three separate occasions when cows were on unrestricted
pasture intake and once when intake was restricted by 50%. On
unrestricted pasture intake, concentrations of Beta-LG were 11% higher in
milk collected after 16h than 8h milking interval, whilst on restricted
intake, concentrations were 44% higher. There were no differences in
concentrations of alpha-lactalbumin (alpha-LA). Both trials show a significant
difference in Beta-LG levels in milk collected after 16h versus 8h milking
interval, although only 71% of all samples collected in the first trial
exhibited this difference and it was less in the second trial using bulk
milk.
Keywords: NZSAPAB;
Diurnal variation; bovine milk; protein composition;
alpha-lactalbumin; Beta-lactoglobulin; Beta-casein.
Last Updated 12-09-1998
