Relationship between milking frequency and free fatty acid level in milk on commercial dairy farms using automatic milking systems

Abstract

On a dairy farm that employed an automatic milking system (AMS), milk wastage occurred due to an unusual rancid flavor. Therefore, we investigated the relationship between milking frequency and free fatty acid (FFA) levels in milk, which could relate to the rancid flavor, on dairy farms that used AMS. The 946 data sets obtained in April 2017

from lactating cows of 8 commercial dairy herds in Kenebetsu (Nakashibetsu, Hokkaido) were analyzed. The cows were classified into 7 groups based on the milking frequency per day (< 2.0, 2.0-2.5, 2.5-3.0, 3.0-3.5, 3.5-4.0, 4.0-4.5, and ≧ 4.5) and the average FFA levels in individual milk samples were compared among the classes. The FFA levels were observed to rise obviously with the increase in milking frequency (P<0.001). The following linear relationship was observed between FFA levels in individual milk samples and milking frequency: Y = 0.486X – 0.077 (r = 0.313, n = 946, P < 0.001), where Y is the FFA level (mmol/100 g fat) and X is the milking frequency (times per day). From this regression equation, the FFA level is calculated to be more than 2.0 mmol/100 g fat when the milking frequency was over 4.3 times per day, which may be a threshold in recognizing the rancid flavor. These results suggest that milking too many times per day is undesirable if the increase in milk FFA levels is to be avoided.