Analysis of major fatty acids in milk produced from high-quality grazed pasture

Abstract

In a survey of milk and pasture samples collected from commercial dairy farms in Canterbury, New Zealand, the results of pasture analysis indicated that levels of water soluble carbohydrates and crude protein were highest in spring and autumn, while the content of neutral detergent fibre was lowest during the same periods. The most notable features of milk fatty acid composition were the high levels of α-linolenic acid (C18:3) and conjugated linoleic acid and the low levels of linoleic acid (C18:2) in milk produced from cows consuming high-quality pasture. It seems likely that this is related to the high proportion of high-quality grazed pasture (mean crude protein = 23.9% of DM; mean water soluble carbohydrates = 16.2% of DM; mean neutral detergent fibre = 39.1% of DM) in the diet. The highest monthly mean value for milk C18:3 was 1.82% of total milk fatty acids for herds fed low levels of supplement in spring (October). This survey shows that there is variation in pasture quality over the season and this was reflected in milk fatty acid profiles.