Fattening pigs at low and high ambient temperatures: Interrelated effects on lying behaviour, adrenocortial activity and vocalisation

Extreme ambient temperatures can pose a significant problem for domestic pigs. On the one hand, they possess few sweat glands, which makes them susceptible to high temperatureson the other hand, they have no thick fur to protect them against the cold. For this reason, domestic pigs are dependent upon behavioural reactions for adapting to the prevailing ambient temperatures. In conventional housing conditions, however, this adaptation is only possible to a very limited extent, if the animals are kept in pens where there is no functional structure in the lying and dung areas, if they cannot freely choose their lying positions because of the limited space available, or if the lying area is not sufficiently insulated for want of straw or a resting kennel. The animals' adaptability, however, does not only depend directly on the conditions in which they are kept, but on other factors as well, such as air humidity and draught in the pens, as well as on the breed, weight, state of health and feed of the pigs. One of the aims of this thesis was to determine whether ethological and physiological parameters could be used to establish temperature ranges in which fattening pigs of different weight classes show no serious adaptations to temperature in a dualsurface pen. The results obtained should also provide guidelines with respect to optimal temperature conditions, which might be used for practical recommendations or even basic legal principles. A further main emphasis is the question of whether the animals' vocalisations, in addition to their lying behaviour and cortisol secretion (both parameters which are very difficult to measure in real-life conditions), may also be used to make statements on their adaptive reactions. The use of vocalisation analysis would have the advantage of enabling automatic monitoring which could be used in real-life conditions. The main study of the project is introduced in the fourth and fifth chapters. Here, the lying behaviour and vocalisation of fattening pigs in three weight classes were recorded at different ambient temperatures relevant to real-life situations (2 ' 29 °C). The animals were kept in the experimental pig house of the Swiss Federal Research Station for Agricultural Economics and Engineering at Taenikon (FAT), in a closed house with a bedded, partially slatted floor. (...) From these results, it can be concluded that the animals should be offered a means of cooling down (such as eg. a shower) when temperatures rise, and an insulating lying area when temperatures fall. The findings of this evaluation were expanded in the second part of the project in the sense that the suitability of vocalisation as an indicator for the adaptive reactions found in the first part was also investigated. (...) With the help of an acoustic monitoring system, it would be possible to implement measures such as the switching on of heat or the making available in a targeted fashion of an insulating lying area or a larger quantity of straw. The use of this method, however, is also possible for additional applications, for example for the assessment of animal welfare in housing conditions which possibly influence the vocalisation of the animals, such as eg. different feeding systems.