Postpartum fever in sows housed in a temporary-confinement farrowing system under tropical conditions: risk factors and associations with feed intake, vaginal discharge, colostrum production, and hematological profiles

Background Temporary-confinement farrowing systems allow sows to move freely but permit short-term confinement to reduce piglet crushing. These systems have been used in Thailand since 2017 to improve sow welfare, but their effects on reproductive performance and postpartum health under tropical conditions remain poorly characterized. This study investigated risk factors for postpartum fever and its associations with feed intake, vaginal discharge, colostrum yield, and hematological profiles. M & M The study included 151 Landrace × Yorkshire sows from a commercial herd in central Thailand. Sows were classified into three parity groups: 1, 2–5, and 6–9. Mean indoor temperatures were 26.9 ± 0.4 °C at 08:00 h and 28.0 ± 0.6 °C at 15:00 h. Sows were housed in a temporary confinement system consisting of a farrowing pen (2.0 × 2.35 m; 4.7 m²) fitted with adjustable swing doors and plastic-slatted flooring. Rectal temperature and respiratory rate were recorded from 3 days before to 3 days after farrowing. As part of the farm’s routine postpartum protocol, all sows received ketoprofen and amoxicillin within one hour after farrowing was completed. Fever was defined as ≥ 39.3 °C prepartum, ≥ 40.0 °C on day 1 postpartum, and ≥ 39.3 °C on days 2–3 postpartum. Feed intake during the first 3 postpartum days was used as an indicator of appetite, and complete blood count parameters were analyzed in 79 sows. Results Fever prevalence increased from 11.3% prepartum to 46.4% postpartum. Postpartum fever was more frequent in primiparous sows (61.7%) than in parity 2–5 sows (37.0%, P = 0.015) and tended to be higher than in parity 6–9 sows (42.0%, P = 0.056). One day before farrowing, respiratory rate was higher in primiparous sows (125.2 ± 4.9 breaths/min) than in parity 2–5 (91.5 ± 4.6) and parity 6–9 sows (87.0 ± 4.7, both P < 0.001). One day postpartum, respiratory rate was higher in sows with fever than in those without fever (97.5 ± 4.2 vs. 85.7 ± 4.0 breaths/min, P = 0.044). Sows with fever had higher colostrum yield (5.39 ± 0.29 vs. 4.55 ± 0.31 kg, P = 0.050), lower feed intake (1.70 ± 0.09 vs. 1.96 ± 0.09 kg/day, P = 0.050), and a greater prevalence of reduced appetite (77.1 vs. 54.3%, P = 0.003). Sows with fever had higher red cell distribution width–coefficient of variation (RDW-CV) (20.5 ± 0.4 vs. 19.2 ± 0.3%) and red cell distribution width–standard deviation (RDW-SD) (50.8 ± 1.5 vs. 45.4 ± 1.1) but lower white blood cell (WBC) count (14.8 ± 1.0 vs. 17.6 ± 0.8 × 10 3 /µL), lymphocyte (6.4 ± 0.9 vs. 9.1 ± 0.7 × 10 3 /µL), and mean corpuscular hemoglobin concentration (MCHC) (32.8 ± 0.2 vs. 33.5 ± 0.2 g/dL) values than those without fever ( P < 0.05). Other hematological parameters did not differ between groups. Anemia, indicated by low red blood cell (RBC) count and hematocrit, affected 78.5% and 77.2% of sows, respectively, but was not associated with fever. Conclusions Overall, postpartum fever was highly prevalent, particularly among primiparous sows, emphasizing the need for parity- and climate-specific management strategies in tropical temporary-confinement farrowing systems.