Broiler chick responses to anorectic agents: dietary acetic and propionic acids and the blood metabolites.

The effects of dietary supplementation with acetic or propionic acid, given at a level of 3% of diets containing 2,500 or 2,750 kcal of metabolizable energy per kg, on levels of blood glucose, and on lipid, protein, and energy metabolisms were studied in female broiler chicks. Voluntary feed and energy intakes, as well as body weight gain, decreased significantly with the inclusion of the acids in either diet, in decreasing order of effect: propionate > acetate > nonsupplemented controls. The relative weight of the abdominal adipose tissue decreased significantly with the inclusion of either acid, but was unaffected by dietary energy level. In contrast, the weight of the liver was higher in birds fed the low-energy diet, but was unaffected by the anorectic agents. Inclusion of the acids increased the concentration of volatile fatty acids in the cecum and blood plasma. The rate of clearance of plasma propionate was greater than that of acetate. Anorectic agents and dietary energy density exhibited a synergistic effect on feed intake. These agents altered blood metabolites involved in lipid and energy metabolisms, but not in that of protein. Plasma metabolites and enzymes, particularly beta-hydroxybutyrate and alkaline phosphatase, reflected the degree of feed restriction, supporting the hypothesis that the hypophagic effect of these acids is due to metabolic intervention.