Between April 2006 and February 2008 plasma long
chain fatty acids (LCFA) profiles were assessed every 8
weeks on individual blood samples from 27 Simmental
cows, with lactation number from 1 to 6 selected from a
dairy herd. Body condition score (BCS) and back fat thickness
(BFT) were measured on the same day as the blood
was taken. Assessment of the variability of plasma LCFA in
relation to the influences of stage of lactation and season
of the year was the main objective of this study.
All of the fatty acids analysed presented differences
(p<0.05) due to the stage of lactation as a factor. Plasma
total LCFA amounts (μg/ml) were higher in early lactation
(1,641.4±513.85) in comparison with late lactation
(1,473.67±336.05) and with dry Simmental cows
(1,208.5±396.55). The sum of plasma MUFA (% of total fatty
acids) was higher in the period of negative energy balance
in early lactation (14.39 ± 4.00) in comparison with
mid (11.79 ± 1.99) and late (11.93 ± 2.14) lactation. Moreover,
the sum of SFA was significantly higher in dry than
lactating cows. Season had an impact on the sum of SFA
(% of total fatty acids) which was higher in winter than
summer, while the sum of ω-3 PUFA was higher in summer
than winter. Also some individual plasma LCFA were significantly
affected by the season and some individual plasma
LCFA were affected by the interaction between stage
of lactation and season of the year. In conclusion, the fatty
acids profiles of Simmental cows were affected mainly by
the stage of lactation and to a lesser extent by the season
of the year.