The role of malabsorption of nutrients in the mechanism of reduction in productions of the ruminants infested with gastrointestinal nematodes has been a controversial question because of the compensatory absorption and reabsorption in distal part of the small intestine. However, during the last decade, leading research showed that malabsorption has a major role in this mechanism because of 1) compensatory absorption and reabsorption remain limited to some nutrients, 2) large quantities of incompletely digested nutrients exceeding the intestine capacity, and 3) poor reutilization of reabsorbed nutrients.