Abstract Gilt development and longevity remain significant challenges for the swine industry. Tracking changes in performance and health across parities from the time a gilt enters the breeding herd enables producers to make informed decisions that may support sow retention in the herd. Blood biomarkers offer valuable insights into an animal’s health, welfare, and nutritional status, and can be linked to sow performance to help indicate potential strategies for improving sow longevity. The objective of this study was to evaluate changes in blood biomarkers in gilts between the farrowing of their first litter and the weaning of their third litter (P2) and associations with litter performance in each parity. Nine gilts were followed from pre-farrowing until the end of weaning of their third parity. Whole blood was collected via the jugular vein at: pre-farrowing, at weaning of P0, P1 and P2, and immediately analyzed using the iCheck Vitamin E (BioAnalyt, Teltow, DE), iSTAT Alinity (Abbott, Park, IL), and VetScan (Zoetis, Parsippany, NJ). Lactation performance was recorded for each parity. Caliper score was recorded at the same timepoints as the blood sampling. Data were analyzed using JMPPro 18.0, with a mixed-model used to evaluate changes in biomarkers over the three parities. Caliper score followed an expected pattern over time, with a tendency to be the highest in gilts pre-farrowing, and the lowest at P0 weaning (P = 0.075). There were no significant changes in litter performance between parities, although number weaned was significantly higher at P1 compared to P0 and P2 (P 0.001). Total protein (P = 0.008), blood urea nitrogen (P = 0.002) and total Ca (P = 0.020) were higher in P1 and P2 weaning than in P0 pre-farrowing and weaning. These biomarkers can be used to indicate organ function, health and nutritional status. Hemoglobin was lowest in P0 at weaning, with highest levels observed in P1 weaning (P = 0.048). Bicarbonate decreased in P0 weaning compared to pre-farrowing and rose again in P1 weaning (P = 0.001). Both hemoglobin and bicarbonate are involved in gas transport and blood buffering capacity. Creatinine decreased in both P0 and P1 weaning compared to PO pre-farrowing, suggesting catabolism during this time. Alkaline phosphatase was the opposite; higher levels in PO and P1 weaning, which could indicate liver/bone issues developing with age. Vitamin E increased with parity, with P1 and P2 weaning having similar levels. Blood biomarker changes suggest nutritional or health opportunities that could be used as indicators in potential strategies for sows in the breeding herd, and this work provides preliminary insights in to blood biomarkers changes over multiple parities. Biomarker status during the first gestation (P0) could be useful to improve future health and performance.
McCormack et al. (2026) studied this question.