Effect of different systems for the control of environmental temperature on the performance of sows and their litters

ABSTRACT

Background: In tropical and subtropical regions, temperature values above thermoneutrality for pigs are often experienced and lactating sows maintained outside the thermal comfort zone might have their performance compromised. The use of ventilation or evaporative cooling to maintain animal thermoregulation might be alternatives to minimise animal production losses. The objective of this study was to evaluate the influence of three different systems for the control of environmental temperature on the productivity of sows and their litters. Materials, Methods & Results: Three systems of environmental temperature control were evaluated air-conditioned AC (n = 79), with farrowing facility temperature controlled by a system of evaporative cooling pads combined with negative pressure ventilation; snout cooler SC (n = 82), with a cold air outlet directed toward sows, combined with management of curtains; and management of curtains MC (n = 83). Piglet weight was recorded at cross-fostering, and at 14 and 20 days of age. Temperature (TEMP) and relative humidity (RH) were measured daily at five time points (800, 1000, 1200, 1400 and 1600 h). The variables concerning the sows were analysed with the MIXED procedure of SAS, including the fixed effect of system and random effects of period and period × system interaction. The weight of piglets, TEMP and RH inside the farrowing facility were analysed as repeated measures using the MIXED procedure. Means were compared with the Tukey-Kramer test. The weight of sows at farrowing, the number of cross-fostered piglets and weight of piglets at cross-fostering were similar among the systems (P > 0.10), with overall means of 241.2 kg, 11.4 piglets and 1.4 kg, respectively. In the AC system, TEMP (23.1ºC) was on average lower (P < 0.05) than in the SC (26.8ºC) and MC (26.8ºC) systems. Overall, higher RH (P < 0.05) was observed in AC (88.3%) than in SC (74.5%) and MC (73.6%) systems. Sows of the MC system had a lower daily feed intake (DFI) than AC sows (P < 0.05) and tended (P = 0.082) to have lower DFI than SC sows (4.7 vs. 5.2 vs. 5.1 kg for MC, AC and SC sows, respectively). There were no differences (P > 0.10) among AC, SC and MC systems regarding sow weight loss during lactation (3.3% vs. 5.0% vs. 4.0%) and weaning-to-estrus interval (4.5 d vs. 5.0 d vs. 4.5 d). The number of weaned piglets was similar among the systems (P > 0.10) with an overall mean of 10.8 weaned piglets. The weight of piglets at weaning tended to be lower (P = 0.083) in the MC than the SC system (5,977 g vs. 6,209 g), whereas piglets of the AC system had an intermediate weight (6,152 g). Discussion: The temperature in SC and MC systems was above the upper critical temperature for sows, mainly between 1200 and 1600, which could explain the lower feed intake of sows in the MC system. The higher feed intake of SC sows compared to MC sows is probably related to the microenvironment created by the fresh air over the heads of SC sows improving their thermoregulation and comfort, and preventing a reduction in feed intake. The AC system was the most efficient in reducing the temperature in the farrowing facility. However, the higher feed intake of AC sows compared to that of MC sows did not result in differences in piglet weight. As the temperature in the AC system was close to the lower critical temperature for the piglets, heating provided to piglets was probably insufficient and they required an extra energetic demand for heat production to maintain their body temperature. The higher weight of SC piglets is probably explained by the higher feed intake of sows and by the fact that temperature in the farrowing facility did not decrease as in the AC system.