New Zealand Journal of Agricultural Research abstracts
Milk harvesting and cow factors influencing seasonal variation in
the levels of free fatty acids in milk from Waikato dairy herds
N. A. Thomson
M. W. Woolford
P. J. A. Copeman
Dexcel
Private Bag 3221
Hamilton, New Zealand
email: norman.thomson@dexcel.co.nz
M. J. Auldist
Department of Primary Industries
RMB 2460, Hazeldean Road
Ellinbank VIC 3821, Australia
Abstract Free fatty acids (FFA) occur naturally in
milk and, under certain on-farm conditions, concentrations increase,
affecting the flavour, processing efficiency, and shelf-life of dairy
products. To obtain some understanding of these, FFA concentration was
determined in silo milk samples collected from seasonal supply dairy
farms in Waikato, New Zealand during the 1997/98 and 1998/99 dairying
seasons. Selected farms represented the major dairy systems: 25 farms
had continuous (rotary) milking systems and 25 farms had batch
(herringbone) milking systems. Four of the herringbone dairies had
milk-harvesting systems that eliminated the air-milk interface (Ruakura
Milk Harvester; RMH). FFA concentrations were assessed every 2 weeks in
bulk milk samples collected from the farm silo. Concentrations of FFA
were lowest in spring (early-lactation) and highest in summer and
autumn (mid–late lactation). The type of dairy design (herringbone
versus rotary) had no association with FFA concentrations, but the four
herds milked by the RMH system tended to produce milk with lower (P
< 0.10) FFA concentrations during summer and autumn 1998/99. A
number of factors were associated with increased FFA concentrations:
type of milking system, milk yield, somatic cell count (SCC), milk
composition, and stage of lactation. Bacterial infection as identified
by SCC and the elimination of the air-milk interface during milk
harvesting (RMH) had possibly major influences on FFA concentrations.
Keywords free fatty acids; milk harvesting;
somatic cell counts
A04019; Received 24 March 2004; accepted 8 December 2004; Online
publication date 21 March 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48:
11–21
0028–8233/05/4801–0011 © The Royal Society of New Zealand 2005
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