Abstract:
Proc. Amt. Sot. Arzim. Prod. 1994 Vol. 20 THE EFFECT OF PLEUROPNEUMONIA AS A STRESSOR ON PIG PERFORMANCE H.J. BRAYA, R. BEHRENDTA, L.R. GILESA, J.M. GOODENA and J.L. BLACK ADcpt. of Animal Science, U nivcrsity of Sydney, Camden, N.S.W. 2570 BCSIRO Division of Anim al Production, Locked Bag 1, Blacktown , N.S.W. 2148 B Chronically stressed pigs perform less well than unstressed pigs and, although the associations between pneum onia and decre are apparent, the role of stress as a mechanism by which performance is reduced is unclear. A mechanistic understanding of disease will allow the AUSPIG decision support software (Black et al. 1986), used in Australian and international piggeries, to better predict the performance of pigs with respiratory disease. This study examines the effect of Actinobacillus pleuropneumoniae serotype 1 (App) challenge on the cortisol response of growing pigs. Five female specific pathogen free pigs (average liveweight 70 kg) were surgically prepared for the measurement of energy expenditure (Giles et al. 1990). The pigs were housed in metabolism crates at a constant temperature (22�C) and in constant light. They were randomly divided into 2 groups; group 1 contained pigs A and B and group 2 contained 3 pigs. To establish a baseline, blood from both groups was collected from the jugular vein at least 6 hours prior to intra-bronchial inoculation. During anaesthesia the pigs were given either 1 x 108 colony forming units of App in 5 mL of media (group 1) or 5 mL of phosphate buffered saline (group 2) into the right lung. Blood was sampled regularly for 50 hours post-inoculation. After 6 days the pigs were euthanased and the lungs isolated and perfused with fixative and lung damage due to inoculation was calculated from image analysis of serial lung slices. Plasma cortisol concentrations were estimated by radioimmunoassay. Figure 1. The effect of right lung damage due to challenge with phosphate buffered saline or ActinobaciZZus pleuropneumoniae on circulating plasma cortisol concentrations in growing pigs. Pig A (closed circles) had right lung damage of 20%. Pig B (open circles) had right lung damage of 80%. Group 2 (triangles) had no right lung damage (n = 3). It can be seen from Figure 1 that all pigs had an initial i ncrease in circulating plasma cortisol levels durin .g inoculation pres umably due to anaesthesia The pigs in group 1 however h ad a sus tained cortisol response when compared to those in group 2. The difference in response of pigs A and B suggests that there may be a relationship between plasma cortisol levels and the the severity of the disease. It is li kely that the circulating cortisol response may have a role in the reduced performance associated with respiratory disease in Australian piggeries. BLACK, J-L., CAMPBELL, R.G., WILLIAMS, I.H., JAMES, K.J. and DAVIES, G.T. (1986). Research and Development in Agriculture 3: 121-45. GILES, L-R., GOODEN, J-M., LORSCHY, M.L., ANNISON, E.F. and BLACK, J.L. (1990). Proc. Nutr. Sot. Aust. 15: 41. 412