The heating-up phase should be managed so that the farrowing pen is at the correct temperature (38–40 °C) by the time the first piglet is born. Depending on the design of the farrowing pen, it should be borne in mind that sows, or sows due to farrow later, in forced-ventilated housing may be exposed to excessive heat. In a closed farrowing pen or farrowing crate, heating generally takes place more quickly and the sow’s ambient temperature is not significantly affected.
The start time for heating depends on the heating capacity and the material that needs to be heated. For materials that heat up quickly, it is sufficient to start shortly (approx. 4–6 hours) before the expected due date.
Check for yourself in both summer and winter how long it takes for the floor to reach the piglets’ body temperature using normal heating output. In summer in particular, the nest should be heated as late as possible, as warmer supply air can quickly cause the temperature for sows to become too high.
An infrared heat lamp can also be useful. The advantage is that it generates heat and light relatively quickly.36 The disadvantage is poor heat distribution, with high temperatures at the centre and a sharp drop in temperature at the edges.
The older the piglets get, the lower their heat requirements become, and it is beneficial for the piglets’ lying behaviour (preventing crushing) to lower the temperatures. A study by Meyer34 found the following regarding the temperature regime:
More than 80% of the piglets were found on the heating pad when the temperature was 39.2 °C in the first week, 37.2 °C in the second week and 36.5 °C in the third week. For older piglets, the room temperature plays a greater role. This fluctuates with the outside climate and, in many pigsties, cannot be regulated, particularly in the range of high temperatures. The average room temperatures were (highly significantly) influenced by fluctuations in the outside climate (averaging 15 °C to 8 °C). On all days when 80–100% of the piglets were found in the farrowing nest, the room temperature averaged 21.2 °C; when average acceptance was only 50%, it was 23 °C; and when average acceptance was 6%, it was over 24 °C. According to Meyer, it is the sow in particular who acts as the ‘pacemaker’ for the lying area, not necessarily the temperature of the floor. Especially at the start of the suckling period, sows make contact with the piglets through grunting sounds to call them to suckle. Consequently, the young piglets frequently stay in the area around the sow’s head and evidently prefer to rest in these spots.
Consequently, when designing the housing, priority should be given to sow-oriented temperature regulation in the farrowing pen rather than precise temperature control of the nests.