The lactose content of milk is an indication of milk quality, particularly in late lactation.

Lactose is a form of sugar that is made by the cow. The average content varies between 4.6% and 4.9% during the lactation. Milk must have a lactose level of 4.2% or greater to be used in the manufacturing process. Penalties are applied if the lactose level falls below 4.2%. Low lactose levels indicate low energy intake and can also be exaggerated by bad weather, poor forage quality, animals in poor body condition, disease and high SCC.

When cows move into late lactation, lactose levels will drop naturally, this coincides with the decline in milk production. This problem is even more pronounced in spring calving herds where all the cows have calved in a 12-week period, and they enter into late lactation at the same time. It is important that cows are managed correctly in terms of diet and that cows are also dried off when their yield reaches less than 10 litres per day. The key steps to maintain lactose over 4.2% in late lactation are:

• maintain a good quality diet in late lactation
• dry off cows producing less than 10 litres per day
• dry off high SCC cows – cows with high SCCs produce low lactose milk at all stages of lactation