Background: Post-weaning diarrhoea (PWD) is a significant gastrointestinal disease in pigs. It is considered a multifactorial disease associated with proliferation of enterotoxigenic Escherichia coli in the intestinal tract of affected pigs. The aim of this study was to analyse risk factors related to the occurrence of PWD on Finnish piglet producing farms.

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Underyearling Arctic charr were acclimated to six temperatures between 6 and 21·5 C and thermal tolerance and resistance were tested after an acclimation period of at least 2 weeks. Resistance times were influenced by acclimation temperature and the highest upper incipient lethal temperature was 23-24 C. An upper limit for cultivation of Lake Inari charr is suggested to be 21 C which is the intercept of the function which represents the upper limit of the thermal tolerance zone. 1997 The Fisheries Society of the British Isles

Underyearling Lake Inari Arctic charr Salvelinus alpinus were acclimated to 11·0 C for 3 weeks, and then one group was maintained at 11·0 C and others were exposed to 14·4 C const , 17·7 C const or a diel fluctuating temperature of 14·3 C 1 C (14·3 C fluc ). Routine rates of oxygen consumption and ammonia excretion were measured over 10 days before the temperature change and over 31 days following the change. Measurements were made on fish that were feeding and growing. The temperature increase produced an immediate increase in oxygen consumption. There was then a decline over the next few days, suggesting that thermal acclimation was rapid. For groups exposed to constant temperature there was an increase in oxygen consumption (M accl , mg kg 1 h 1 ) with increasing temperature (T), the relationship being approximated by an exponential model: M accl =46·53e 0·086T . At 14·3 C fluc oxygen consumption declined during the 3-4 days following the temperature shift, but remained higher than at 14·4 C const . This indicates that small temperature fluctuations have some additional influences that increase metabolic rate. Ammonia excretion rates showed diel variations. Excretion was lower at 11 C const than at other temperatures, and increases in temperature had a significant effect on ammonia excretion rate. Fluctuating (14·3 C fluc ) temperature did not influence ammonia excretion relative to constant temperature (14·4 C const ). 1998 The Fisheries Society of the British Isles