The effect of once-a-day (OAD) milking on milk composition has been variable. In the four-year breed by milking frequency comparison, the following results were observed:

• Milk fat concentration: Friesian OAD - higher concentration in two years, lower in two years Jersey OAD - 0.2% unit higher concentration in all years
• Milk protein concentration: 0.12-0.18% unit higher concentration for all OAD cows
• Milk lactose concentration: 0.15% unit lower concentration for all OAD cows.