Gastric Emptying Regulates the Kinetics of Nitrogen Absorption from 15N-Labeled Milk and 15N-Labeled Yogurt in Miniature Pigs

Abstract

Thirty-six miniature pigs divided into two groups of 18 animals were fed 15N-labeled milk or yogurt. Polyethylene glycol 4000 was added to the diets as a non-absorbable marker of the liquid phase. Animals were slaughtered 1, 2, 4, 8 and 12 h after meal ingestion, and the gastrointestinal tract was removed and divided into 10 parts. Polyethylene glycol, total nitrogen and 15N enrichment were measured in the digesta. Both the intestinal delivery of the liquid phase and the nitrogenous fraction of the chyme were delayed more in pigs fed yogurt than in pigs fed milk. No stimulatory effect of diet ingestion on endogenous nitrogen secretion was found. Both milk proteins and yogurt proteins were highly digestible: 93% of the exogenous nitrogen disappeared 12 h after feeding. The kinetics of exogenous nitrogen delivery into the intestine was correlated (r = 0.999 for milk and r = 0.974 for yogurt) with that of exogenous nitrogen absorption. These results suggest that milk proteins are rapidly absorbed after they reach the intestine. Gastric emptying is a major factor controlling the kinetics of milk nitrogen absorption.

Postprandial intestinal and whole body nitrogen kinetics and distribution in piglets fed a single meal

“…Using an intrinsically labeled 15 N meal, we found that the real cecal digestibility of the formula milk protein was 94%, a value close to those already found for milk protein in piglets or minipigs (18,33) and consistently slightly inferior to the apparent protein digestibility (ϳ98%) measured in piglets (35,42). When summing these cecal losses and the transfer of dietary N to urea production, we were able to estimate that the whole body postprandial retention of dietary N is 90% of the ingested amount over 8 h, which represents a high efficiency of utilization.…”

Portal absorption of 15N and amino nitrogen in the growing pig after ingestion of labelled milk, yogurt or heat-treated yogurt

“…This result is undoubtedly related to the different intestinal emptying rates between milk, yogurt and heat treated yogurt as has been suggested by several authors [7,8,33,35]. Since the viscosity differences between milk and live yogurt result in a slower gastric emptying rate for yogurt [33], it is understandable that the portal absorption profile of 15 N and AN is for live yogurt (Y0 and Y21) when compared to M and HY.…”

“…Thus storage of yogurt at 4 °C did not modify the nutritional characteristics of yogurt. disappearance (ingested minus recovered exogenous nitrogen) in the lumen [7,8]. These authors particularly noticed that the highest exogenous jejunal nitrogen contents were measured 20 min after milk ingestion and 60 min after yogurt ingestion.…”

Mesure de la digestibilité des protéines par la méthode des différences porto-artérielles chez l’espèce porcine

“…Ils ont constaté que l'azote exogène commence à être absorbé au cours des 20 premières minutes suivant l'ingestion orale de la caséine. L'absorption des constituants du lait et du yaourt a été étudiée à partir de leur disparition nette dans l'intestin grêle [13,14]. Ces auteurs ont noté que dans le contenu jéjunal la teneur maximale en azote exogène a été mesurée 20 minutes après l'ingestion de lait et 60 minutes après l'ingestion de yaourt : une vidange gastrique plus lente pour le yaourt expliquerait ce décalage.…”

“…Le lait et le yaourt thermisé sont principalement absorbés pendant les 2 premières heures après l'ingestion, tandis que l'absorption du yaourt est prolongée au cours des 240 min de la période postprandiale. Ces résultats peuvent être expliqués par des différences de rythmes de vidange gastrique comme cela a été suggéré par plusieurs auteurs [14,38,39,47]. Le paramètre 15 N utilisé pour évaluer l'absorption portale des protéines des produits laitiers apparaît comme un indicateur valable puisqu'il permet d'établir le profil d'absorption spécifique de l'azote du lait ou des produits laitiers.…”