Raw milk contains natural compounds, such as lactoferrin, with anti-microbial activity. These compounds may constitute a form of protection against the proliferation of spoilage and potentially pathogenic microorganisms, as well as being potentially beneficial for health. The objective of this study was to determine the influence of the cows' diet on the concentration of this compound in milk. An experimental herd of 32 Montbeliarde dairy cows was split in two groups, ensuring an equal balance according to the stage and lactation period. The first group grazed natural pasture, and the second was fed dry feed (35% hay and 65% ground barley/soya-bean meal). The results obtained showed that the lactoferrin content was significantly higher in milk from cows fed with hay and meal (292.8 +/- 34.0 mu g/ml) than from cows fed with grass (159.7 +/- 12.2 mu g/ml). These results suggest that it may be possible to naturally increase the concentration of lactoferrin in milk through appropriate management of the cows' diet.