In Belgium research by the Flemish ILVO institute shows that cows that get less concentrate feed after 80 days in lactation use this more efficiently. Cows that got 1 kilogram of concentrate per 1.7 kilogram of extra milk and heifers that got 1.6 kilogram of concentrate per extra kilogram of milk were compared with 1 kilogram of concentrate per 3 kilogram of extra milk. With cows this did not result in a lower milk production, fat or protein content. In heifers it did. However: other effects, such as fitness, health and fertility, were not considered.