The effects of acute simultaneous exposure to ammonia on the detection of buried odourized food by pigs

The present study is the first in a series designed to determine whether or nor acute or chronic exposure to ammoniated atmospheres compromises olfact ory perception in the pig. Herein, we focused on acute effects of ammonia o n food location. As a prerequisite, the relative consumption of a range of 15 odourized visible foods by eight Duroc X Landrace pigs (Sus scrofa) was examined over 15 days in Experiment 1. This enabled us to identify the most and least preferred types for later use in olfactory perception tasks in E xperiments 2 and 3, Five of these odourized foods are categorised by humans as sweet (almond oil, peach, raspberry, strawberry and vanilla), six as bi tter (anise oil, benzaldehyde, caffeine, cetyl pyridium chloride, eugenol a nd sucrose octaacetate) and three as sour (acetic acid, butyric acid and pr opionic acid). A control food treated with de-ionized water was also includ ed. A 250-g sample of each of eight food types was presented in eight food bowls tone sample per food bowl) positioned along the sides of a square pen . Water was available ad libitum, Pigs were tested individually for 30 min. An analysis of variance (ANOVA) showed that the pigs consumed significantl y less food when it was treated with eugenol, anise oil or benzaldehyde rat her than any of the other odourants (P < 0.001). A hierarchical cluster ana lysis of actual food consumption grouped these 'bitter' foods into two sepa rate categories and grouped all 'sour' foods together. The other foods were placed into two other clusters, though consumption of the unodourized cont rol, the 'sweet' and the remaining 'bitter' foods did not differ significan tly from that of 'sour' odourized foods (P > 0.05). The cluster analysis al so showed individual differences in the preferences of the pigs for some of the most and least preferred foods. Experiments 2 and 3 addressed the ques tion of whether acute, simultaneous exposure to 40 ppm ammonia would compro mise the pigs' ability to locate buried, odourized wafer paper food parcels . Food parcels were treated with either almond oil or benzaldehyde, which h ad been identified in Experiment 1 as among the most and the least preferre d odourants, respectively. A control parcel filled with wheat straw was als o presented. All parcels were buried under wheat straw in an octagonal expo sure chamber. In Experiment 2, three parcels of the same type were buried i n six compartments of the chamber. The pigs were given 3 min in each compar tment to find these parcels. In Experiment 3, one parcel of each type (i.e. , almond oil, benzaldehyde and control) was buried in each of the eight com partments and, this time, the pigs were given only 1 min in each compartmen t to find the parcels. In both experiments, half of the compartments were f illed with fresh air while the other half were polluted with approximately 40 ppm of ammonia. Whereas the pigs rapidly found most of the odourized par cels, they uncovered very few of the controls (P < 0.001). Unlike the resul ts of Experiment 1, the pigs no longer expressed a preference for either od ourized food (P > 0.05). Testings in an ammoniated atmosphere did not affec t the number of parcels of each type found or the latency to find them (P > 0.05). Thus acute simultaneous ammonia exposure had no hyposmic or hyperos mic effect on the detection of buried odourized food. (C) 2000 Elsevier Sci ence B.V. All rights reserved.