Exposure to environmental stressors result in increased viral load and further reduction of production parameters in pigs experimentally infected with PCV2b.

Porcine circovirus type 2 (PCV2) has been identified as the essential, but not sole, underlying infectious component for PCV-associated diseases (PCVAD). Several co-factors have been suggested to convert an infection with PCV2 into the clinical signs of PCVAD, including co-infection with a secondary pathogen and the genetic background of the pig. In the present study, we investigated the role of environmental stressors in the form of changes in environmental temperature and increased stocking-density on viral load in serum and tissue, average daily weight gain (ADG) and food conversion rate (FCR) of pigs experimentally infected with a defined PCV2b strain over an eight week period. These stressors were identified recently as risk factors leading to the occurrence of severe PCVAD on a farm level. In the current study, PCV2-free pigs were housed in separate, environmentally controlled rooms, and the experiment was performed in a 2×2 factorial design. In general, PCV2b infection reduced ADG and increased FCR, and these were further impacted on by the environmental stressors. Furthermore, all stressors led to an increased viral load in serum and tissue as assessed by qPCR, although levels did not reach statistical significance. Our data suggest that there is no need for an additional pathogen to develop PCVAD in conventional status pigs, and growth retardation and clinical signs can be induced in PCV2 infected pigs that are exposed to environmental stressors alone.

Development and application of a novel environmental preference chamber for assessing responses of laboratory mice to atmospheric ammonia.

A novel environmental preference chamber (EPC) was developed and used to assess responses of laboratory mice to atmospheric ammonia. The EPC features 1) a test chamber with 4 individually ventilated, mutually accessible compartments; b) automated tracking of mouse movements by using paired infrared sensors; c) identification of individual mice by using photosensors; d) monitoring and regulation of the NH3 concentration in each compartment; and e) personal-computer-based data acquisition. In an initial preference study with the EPC, 4 groups of 4 laboratory mice (BALB/c/Bkl; body weight, 13.4 to 18.4 g) were each given a choice among 4 NH3 concentrations (mean +/- SE) of 4 +/- 2, 30 +/- 2, 56 +/- 4, and 110 +/- 6 ppm for 2 d after a 2-d familiarization period. Once trained to use the intercompartment tunnels, the mice made extensive use of the EPC, with each group making more than 2000 intercompartment movements during 48 h. Video recording verified the results of the automatic tracking system, which detected and correctly determined mouse location for 79% of the moves. The use of photosensors proved to be ineffective in recognizing individual mice. Although the EPC would benefit from refinement and further development, it simplified analysis of locomotion behavioral data. Results of the preference study indicated that the mice exhibited no clear preference for, or aversion to, any of the experimental concentrations of ammonia and that the mice clearly preferred the upper 2 compartments of the chamber over the lower 2 compartments. Further investigation should be conducted to verify these preliminary results and explore other preferences of laboratory mice for environmental conditions and resources.

Behavioral correlates of olfactory and trigeminal gaseous stimulation in chickens, Gallus domesticus.

Despite growing evidence of avian olfactory abilities, there are few reports of behavioral correlates of chemosensory stimulation in birds. The present study aimed to determine how the behavioral responses of hens to selected gases might be affected by input from different chemosensory systems. We also hoped to relate electrophysiological thresholds previously measured in our laboratory to behavioral evidence of perception. Immediate behavioral responses to ascending series of short (7 s) pulses of olfactory (hydrogen sulphide), trigeminal (carbon dioxide) and combining (ammonia) gaseous stimulants were measured in 12 partially restrained adult hens (Gallus domesticus) using a purpose built gas delivery system. The concentration ranges applied matched those used in our previous electrophysiological studies of olfactory bulb responses. Consistent and specific behavioral responses were observed in response to stimulation with each gas. While significant increases in mandibulation (a distinctive rapid bout of bill movements), interruption of ongoing behavior, orientation to the end of the stimulus, and struggling were seen during stimulation with all three gases, orientation towards the stimulus occurred only in response to the olfactory stimulants, ammonia and hydrogen sulphide. The only gas to elicit significant avoidance was hydrogen sulphide, while gasping and headshaking were elevated in response to stimulation with carbon dioxide. Approximate threshold values for some types of behavior related reasonably well to receptor thresholds determined electrophysiologically, but perception may have occurred at lower concentrations without overt behavioral consequences. The diversity of the behavioral responses observed supports the notion that the gases selectively stimulated different sensory pathways.