Behavioural and physiolgical thermoregulation in groups of pregnant sows housed in a kennel system at low temperatures

The behavioural and physiological responses of pregnant sows to cold exposu re in a kennel system were investigated. Ten groups, each of six pregnant s ows, were housed over winter in a non-insulated building containing kennels . Lying posture, social thermoregulation, time spent inside the kennels and general activity were recorded in three 48-h periods with different diurna l room temperatures: cold (-9 to -1 degrees C), medium (0 to +3 degrees C) and warm (+4 to +9 degrees C). Blood samples were collected from two of the groups, and the concentrations of glucose, free fatty acids, total thyroxi ne (TT4) and free thyroxine (FT4) in the plasma were determined. The air temperature difference in between the surrounding room and the kenn els increased with decreasing room temperature with a maximum of 12 degrees C at a room temperature of -10 degrees C. Activity level did not differ si gnificantly between temperature periods (30.6 +/- 1.1%). At all temperature periods, the sows spent between 80 and 90% of their time inside the kennel s. The sows spent significantly more time eating/manipulating straw in the cold than in the medium and warm period (P = 0.038). Time spent lying on th e belly in body contact with other sows inside the kennel increased signifi cantly from 15.6% in the warm period to 20.3% in the medium period and 44.9 % in the cold period (P = 0.001). The two highest ranked individuals (rank 1 and 2) tended to spend more time inside the kennel than sows with rank o rder 4 to 6 (P = 0.059). At a diurnal room temperature of -8 degrees C, the sows had a significantly higher level of (FT4) in the plasma than at highe r temperatures (P < 0.001). The relationship between the other blood parame ters and diurnal room temperature was difficult to interpret. This study suggests that kennels with straw give the sows good protection f rom climatic conditions, and that social thermoregulation in a micro enviro nment is an important strategy to cope with low temperatures. At a diurnal room temperature of -8 degrees C, however, the increase of FT4 in the plasm a may indicate an increased metabolism and thus an increased energy require ment. Since low-ranking individuals spent less time inside the kennels than high-ranking sows, they probably had a greater heat loss. For practical ap plication of the system, the kennel should thus be designed in a way that a llows all individuals to get inside.