1. Male birds of a laying strain had permanent catheters introduced into the hepatic portal vein via the coccygeo-mesenteric vein. 2. Infusions of 5 ml of 40, 100 or 150 g glucose/l solution over 2 min caused a non-significant depression of food intake compared with a 9 g NaCl/l control solution. 3. Infusions of a range of isotonic glucose solution (0 to 60 g glucose/l, 30- mosm) at 1.4 ml/min over 3 h caused food intake depression within the 3-h period (P less than 0.01) proportional to the logarithm of the dose. 4. This effect was not observed when 60 g glucose/l was infused at the above rates into the jugular vein. 5. Starvation of the bird for 21 h accentuated the depressive effect of glucose load on food intake, especially when birds were not given food until after the 3-h infusion. 6. The infusion of solutions of sodium chloride (1.0 to 13.0 g/l, 33 to 433 mosmoles/kg) at 1.4 ml/min over 3 h stimulated food intake within the range of 3 to 7 g NaCl/l (100 to 233 mosm) but suppressed intake outside this range. This can be interpreted as a possible interaction with water intake control. 7. Infusion of 20 ml of glucose solution (0, 18 or 54 g/l) over 5 min into the crop and 0, 3.75 or 60 g glucose/l at 1.4 ml/min over 3 h into the hepatic portal vein, caused an additive, linear depression of food intake.

1. Infusions of 10 g of diet mashed in 20 ml of water, increasing glucose loads and hypertonic solutions of glucose, sorbitol and KCl, were introduced into the crop of the adolescent cockerel (1.5 to 2.0 kg body weight and 12 to 20 weeks of age). All caused a significant reduction of food intake over the following 3-h period. 2. Duodenal infusions of hyperosmotic solutions of sorbitol and KCl at 3 osm significantly decreased food intake within an hour of infusion. Glucose infusion decreased intake only in birds starved for 3 h before the experiment. 3. The results are discussed in relation to the site of infusion and nutritive visceral mechanisms of food intake control. It is likely that there is a major osmotic control in the duodenum which may affect a secondary control system in the upper gastro-intestinal tract.

The hepatic portal veins of cockerels were catheterised to study the effects of 3-h infusions of nutrient solutions on voluntary food intake. An amino acid mixture, infused at rates up to 800 mg N/3 h, depressed intake of a standard diet in a significant linear manner (intakes with the highest dose and control: 1.6 g and 22.6 g/3 h respectively). Infusion of the highest dose into the jugular vein had a smaller and nonsignificant effect (17.2 and 25.3 g/3 h). The effects of combined infusion of amino acids and glucose into the portal vein on food intake were approximately additive.