61 Low sow hemoglobin status is a risk factor for sow removal in commercial herds.

Abstract The increasing reproductive demands of highly prolific sows may contribute to metabolic challenges, including anemia. Hemoglobin (Hb), a key biomarker of iron status, is essential for oxygen transport and overall health; however, its relationship with sow removals and reproductive efficiency remains under-explored in commercial production systems. This study aimed to evaluate the association between late gestational Hb and subsequent sow removals in commercial swine herds. This experiment enrolled 1,945 sows (parities 0–8) from four U.S. commercial herds. Blood was collected from each female via an ear vein prick on 100 ± 12 days of gestation and analyzed on-farm using the HemoCue Hb 201+ device to measure Hb. Females were classified as non-anemic (Hb ≥ 10 g/dL; n = 792 females) or anemic (Hb < 10 g/dL; n = 1,153 females). In addition, perineal score and body condition measured with the Knauer sow caliper version 2 (KSC) were recorded at the time of Hb sampling. Reproductive performance was assessed in the subsequent farrowing event, and sow removals—including deaths, euthanasia, and other non-age-related removals—were tracked for 70 days post Hb testing. A survival model using the PROC PHREG procedure in SAS 9.4 was employed to assess the relationship between sow Hb and sow removal risk, while a linear mixed model using the PROC MIXED procedure was used to evaluate the fixed effects of Hb status, parity, and farm on reproductive outcomes. Anemia prevalence varied by farm (52–65%) and averaged 59.3% across all four farms. Anemia prevalence increased with parity (P < 0.001), occurring in 40.6% of parity 0 females, rising to 82.7% by parity 3. Anemic females had lower body condition than non-anemic females (12.5 vs. 13.1 KSC, P < 0.001), with a positive correlation found between Hb and body condition (r = 0.21; P < 0.001). Anemic sows had more total piglets born than non-anemic sows (16.4 vs. 15.7; P < 0.001). However, anemic sows had a higher stillborn rate (5.3 % vs. 4.2%; P = 0.011), and no differences were found in the number of piglets weaned. Sow removal rates were more than two-fold greater in anemic than in non-anemic sows (8.4% vs. 3.5%; P < 0.001), with each 1 g/dL increase in Hb reducing removal risk by 43% (HR = 0.57;P < 0.001). Sow removal rates were higher in anemic sows within most parities; parity 0 (anemic: 15.4%; non-anemic: 6.9%), parity 1 (anemic: 8.3%; non-anemic: 2.8%), parity 2 (anemic: 13.5%; non-anemic: 6.7%), and parity 3 (anemic: 11.3%; non-anemic: 4.2%) (P < 0.05). Sow removal rates in parity 4+ sows were similar (anemic: 12.1%; non-anemic: 10.3%). These findings highlight anemia’s impact on sow retention and productivity, while additionally suggesting that successive reproductive cycles contribute to declining iron status.