The results illustrate that the lysine and threonine level in the diet of lactating sows affects the amount of these in milk, especially at the beginning of lactation. The level of dietary crude protein has a similar impact. A reduction in the nutrient levels in the diets results in reduced milk production and in a change in the content of nutrients in milk. The performance of piglets is than lower. Increased level of these nutrients positively affects the composition of milk, but it does not affect always a better performance of piglets.