Comparison of the milk fatty acid composition from dairy cows fed high-sugar ryegrass, low-sugar ryegrass, or maize

Ryegrass with high contents of water-soluble carbohydrates (WSC) was recently bred and tested for its potential beneficial effects as feed for ruminants. The objective of the present study was to determine the effect of feeding high-WSC ryegrass hay on the fatty acid composition of the milk as compared to low-WSC ryegrass hay and a maize silage-based diet. The diet type had no significant effect on feed intake and gross milk composition. Milk yield was highest for cows fed the low-WSC hay. Vaccenic acid and conjugated linoleic acids were higher in the milk fat of hay-fed cows compared to those receiving the maize diet. Milk fat from cows fed low-WSC hay showed the highest proportion of α-linolenic acid, while that from cows fed the maize diet showed the lowest proportion. Total polyunsaturated fatty acids were also highest in milk from cows fed low-WSC hay and lowest in milk from cows fed the maize diet. The milk from cows fed the high-WSC hay showed intermediate values for both. In conclusion, the high-WSC hay diet compared to the low-WSC hay had no beneficial influence on the proportion of functional fatty acids in cow milk.