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statistically significant. The correlation between milk production and
concentrations of glucose and urea v.subcut.abdominis is negative. The
value of NEFA and BHB in the same vein, do not show a significant
correlation with milk production. A significant correlation was found
between milk yield and the difference between the values of glucose,
NEFA and BHB measured in two veins. Greater the difference in glucose
concentration between the two veins means greater milk production
(positive correlation), and the greater the difference in concentration of
NEFA and BHB between two veins negatively correlated with milk
production. Since the concentration of metabolites in v.subcut.abdomnis
depends on the use of these metabolites in the mammary gland, we can
conclude that the difference in concentration between the metabolites in
v.jugularis and v.subcut.abdominis arises from the use of metabolites in
the mammary gland. This leads to the further conclusion that the greater
use of glucose in the mammary gland during heat stress leads to increased
milk production, and increased use of fatty metabolites decreased milk
production, while higher concentrations of urea has a negative impact on
milk production. Reduced blood glucose concentration, elevated
concentrations of urea and increased utilization of NEFA and BHB in the
udder may be associated with reduced milk production in cows during heat
stress.
Key words: cows, heat stress, milk production, metabolism.
Primljeno: 10.09.2012. godine
Prihvaćeno: 20.09.2012. godine
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