Effect of phenological phase of dry grazing pasture on fatty acid composition of cows' milk

The fatty acid content is a very important feature of the milk that affects the health of consumers. The aim of this study was to estimate cow's milk fatty acid composition in early vegetative, late vegetative and reproductive phase, with the simultaneous determination of the pasture biomass chemical and botanical composition. The research was conducted on Agrostis castellana semi-natural dry grassland in the vicinity of Podgorica, Montenegro. Cows were put to grazing during the whole experimental period. This pasture was assessed as moderate to good quality and botanically diversified. The chemical composition of the grassland biomass changed with the maturity phase. A significant increase in the content of DM, crude fiber, fat and a decrease in crude protein content were determined throughout three phenological phases (p < 0.05). The content of total milk fat did not show significant variability during first two phases, but it did in the third phase. The content of milk fat and protein was high in all phases, although it is a dry pasture with a poor quality of biomass in the third phase. The content of majority saturated fatty acids (SFAs) increased with grass maturity, while total content of monounsaturated fatty acids (MUFAs) decreased. The polyunsaturated fatty acids (PUFAs) content kept the same level up to the reproductive phase. The phenological phase significantly influenced the content of fatty acids in the third phase (p < 0.05). A notable number of SFAs, MUFAs end PUFAs had the highest content in the second phase.