New Zealand Journal of Agricultural Research abstracts
Variation in the composition of milk protein from pasture-fed dairy cows in
late lactation and the effect of grain and silage supplementation
T. R. MACKLE
A. M. BRYANT
S. F. PETCH
R. J. HOOPER
M. J. AULDIST*
Dairying Research Corporation Ltd
Private Bag 3123
Hamilton, New Zealand
Abstract Sources of variation in milk protein composition
were determined after approximately 203 days-in-milk for spring-calving
Friesian cows grazing ryegrass-white clover pastures in New Zealand. Three
groups each of 15 multiparous cows were managed as separate herds. Each herd
was subjected to one of three management strategies: pasture only, pasture
supplemented with 2-3 kg cow-1 d-1 maize grain, and
pasture plus 5-6 kg cow-1 d-1 maize grain and 3-4 kg
cow-1 d-1 pasture silage. During a 3-week period
beginning in February 1994, milk samples were collected twice-weekly from
individual cows and the detailed protein composition determined. Variation was
observed in milk yield and the concentrations of all protein components
measured, with between-cow variation being greater than within-cow variation
for all parameters except non-protein N and urea. Supplementing pasture with
maize grain and/or silage increased milk yield but had only minor effects on
protein composition. These data will enable increased efficiency of
experimental design in this research area, and provide details of the natural
variation in milk protein composition. This variation gives an indication of
the extent that milk protein composition could be manipulated by on-farm
practices, or through the selection of cows with defined milk protein
profiles.
Keywords milk; protein; cow; variation; nutrition; casein;
whey; pasture
New Zealand Journal of Agricultural Research, 1999, Vol. 42: 147-154
0028-8233/99/4202-0147 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (624K); (scanned from paper original: notes about this process)
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