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The contamination of pastures by polycyclic aromatic hydrocarbons (PAHs) from vehicular emissions is the first step of the contamination of the food chain including the grazing ruminants producing dairy food. In this study, we measured PAH concentrations in grass exposed for 30 days and for 75 days using a standardised culture of Lolium perenne. This method allowed the comparison of the grass contamination between two sites of different daily traffic (highway and rural road) and two control sites: isolated pasture and climate chamber. The results showed that total PAH concentrations ranged from 18 ng/g DW to 414 ng/g DW (DW: dry weight). The highest concentration was detected along the rural road and appeared not to be directly linked to the vehicular flow but probably to the driving cycles of the vehicles. The PAH concentrations were not found to be time-dependent as the values remained similar for the ryegrass exposed for 30 days or 75 days.

The aim of this experiment was to determine portal absorption of calcium in the growing pig after ingestion of extrinsic labelled 45 Ca milk. Portal levels of 45 Ca are high very soon (15 min) af- ter ingestion of milk and decrease after 60 min. The absorption peak was observed at 30 min. The highest porto-arterial differences were observed between 15 and 60 min, indicating that absorption mainly occurs during the first hour (about 48%). 45 Ca portal absorption rate is close to 76%; it indi- cates that the major part of the calcium is absorbed in the first four postprandial hours. Absorption / calcium / milk / pig

The aim of this experiment was to study 15 N and amino-nitrogen (AN) portal absorption in the growing pig after ingestion of uniformly (0.2509 APE) labelled 15 N milk (M), yogurt ingested just after manufacturing (Y0), yogurt stored for 21 d at 4 °C (Y21) and heat-treated yogurt (HY). The highest porto-arterial differences (PAD) in 15 N and AN were found in the period between 30 min and 90 min after ingestion. The absorption of nitrogen from M and HY mainly occurred during the 0-120 min time period (about 70% for M and 67% for HY). For Y0 and Y21, a larger displayed absorption period over the 0-240 min time period was observed. Y0 and Y21 presented a quite sim- ilar portal absorption profile. The 15 N absorption rate was close to 80% for each studied milk prod- uct, suggesting that under our experimental conditions, dairy products (M, Y0, Y21 and HY) deliver nearly the same amounts of nitrogen to the organism. AN absorption rates were around 78% with a higher variability between the milk products. These results also indicate that most of the proteins were absorbed within the 240 min postprandial period. absorption / milk / yogurt / pig

En vue d'effectuer des etudes sur la digestion des proteines laitieres chez l'humain, du lait marque au 15 N a ete produit en incorporant du sulfate d'ammonium marque dans la ration de vaches laitieres. Les vaches ont recu une ration complete distribuee a volonte, contenant 300 g de sulfate d'ammonium. Dans l'essai 1, trois vaches ont recu une dose unique de 50, 150 ou 300 g de sulfate d'ammonium marque en substitution a une dose egale de produit non marque. Dans l'essai 2, trois vaches ont recu 300 g de sulfate d' ammonium le 1 er jour, puis 150 g 24 h et 150 g 48 h apres le premier apport. Les quantites d'aliment ingerees, la production laitiere et la composition azotee du lait ont ete mesurees individuellement. Les cinetiques d'evolution de l'enrichissement en 15 N des fractions azote total, azote soluble et azote caseique du lait ont ete suivies. Dans l'essai 1, l'enrichissement en 15 N du lait est maximal 36 h apres ingestion du produit marque, respectivement 115, 491 et 980 ‰ pour les doses 50, 150 et 300 g. Dans l'essai 2, l'administration de doses repetees de sulfate d'ammonium marque au 15 N amene a un plateau d'enrichissement observe de 36 a 84 h apres la premiere distribution du produit marque. Dans les deux essais, l'enrichissement de la fraction azote soluble (SN) du lait est plus rapide que l'enrichissement de l'azote total (TN). La quantite totale de 15 N retrouvee dans le lait au cours des 7 a 8 jours suivant le premier apport represente en moyenne 16 % de 15 N administre.