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Influence of Meal Frequency on Postprandial Variations in the Production and Absorption of Volatile Fatty Acids in the Digestive Tract of Conscious Pigs¹

Laboratoire de Physiologic de la Nutrition, INRA, France and Istituto di Alimentazione e Nutrizione Animale, Milano, Italy

Abstract

Five Large White pigs of 62.2 ± 1.4 kg mean body weight were fitted with permanent catheters in the portal vein and carotid artery and with an electromagnetic flow probe around the portal vein to study the absorption of volatile fatty acids (VFA) by measuring the concentration of these metabolites in hourly blood samples, and by determining the portal blood flow rate for a period of 12 h after intake of a single 800-g meal (6% crude fiber) preceded by 12 or 24 h of fasting. The portal concentration of VFA mixture always highly exceeded the arterial concentration. The arterial concentrations of propionic, butyric, valeric and isovaleric acids were nearly null, accounting for an almost complete uptake of these VFA by the liver. Acetic acid also was taken up, but to a lesser extent. Total VFA absorption during 12 h was 64% higher (P<.05) after 12 h (1,160 ± 100 mmol/12 h) than after 24 h of preprandial fasting (740 ± 83 mmol/12 h). It increased after the meal (P<.05) from 82.3 ± 7.8 mmol/h between the first and fourth hour to 107.8 ± 7.5 mmol/h between the fifth and tenth hour when the preprandial fasting lasted 12 h; a nonsignificant increase also was found when fasting prior to the meal lasted 24 h. The composition of the VFA mixture was not modified by the length of preprandial fasting. With this type of diet there was a large predominance of acetic acid (52%) followed by propionic and butyric acids (36 and 8.5%, respectively). In feeding conditions of two meals per day, the absorption of VFA in a 60-kg pig represented about 30% of the energy requirements for maintenance. After a single 800-g meal, the 12-h absorption of VFA ranged from 400 to 450 mmol, i.e., 120 to 140 kcal.

¹ Appreciation is expressed to Kirsten Rérat for her help in translating the manuscript into English, to J. Gallé for preparation of graphs and to J. Brachet, F. Cointepas and J. Weber for care of experimental animals.

² Request reprints from Laboratoire de Physiologie de la Nutrition, INRA-Centre de Recherches Zootechniques, 78350 Jouy-en-Josas, France.

³ Istituto di Alimentazione e Nutrizione Animale, Facolta di Medicina veterinaria. Via Celoria 10, 20133 Milano, Italy.