| Popis: |
The objective of the experiments was to investigate the influence of the duration of exposure to different environmental temperatures on the heat production (HP) of growing pigs. 5 trials were carried out with Landrace castrated male pigs at temperatures of 6, 12, 18, 24 and 30 °C. Each trial lasted 9 weeks and four animals with an initial live weight (LW) of 47 ± 2.5 kg were involved. The animals were housed individually. The diet contained 15 MJ ME/kg DM and 19% crude protein. The feeding level was 2.9-times maintenance energy requirement. HP of the pigs kept at 6 and 12 °C was higher than in pigs kept at 18, 24 and 30 °C. Over the time of the experiment HP decreased in all cases, but the extent of the decrease was higher at 6 and 12 °C (15 and 17%, respectively). The coefficients of a regression relating daily HP (all values adjusted to a ME intake of 1292 kJ/kg LW 0.75 · d) to time (week) were: −21.5 (6 °C); −20.3 (12 °C); −4.2 (18 °C); −6.5 (24 °C); −5.3 (30 °C) kJ/kg LW 0.75 · d · week. It was concluded that over the time of the trials a reduction of the thermoregulatory part of the HP takes place. Investigations on the morphology of the body core after slaughter showed a marked increase of longer bristles of the pigs kept at 12 °C, than in pigs kept at 24 °C. The thickness of dorsal fat was also higher. The results show that an important mechanism of acclimation to a cold environment in pigs is the increasing body insulation which leads to a reduction of energy losses for thermoregulatory responses. |
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