Backfat thickness at first insemination as a determinant of endocrine regulation of appetite during the gestation–lactation transition in primiparous gilt

The gestation-lactation transition involves high metabolic demand, and backfat thickness (BFT) better reflects adiposity and endocrine function than body weight (BW). This study evaluated the relationships between body condition indicators (BFT and BW), daily feed intake (DFI), and metabolic and endocrine markers during the gestation-lactation transition in primiparous gilts. Metabolic and endocrine indicators of energy balance were assessed, and their associations with body condition and feed intake were analyzed using correlation analyses and regression models. Sows with greater BFT at first insemination exhibited lower DFI during lactation (3.1 vs. 4.2 kg; P < 0.05) compared with sows with lower BFT. At farrowing, these sows showed higher leptin concentrations (3.2 vs. 2.1 ng/mL; P < 0.01) and higher HOMA-IR values (5.5 vs. 3.6; P < 0.05), whereas ghrelin concentrations were lower (246.9 vs. 305.0 pg/mL; P < 0.05). In contrast, classification by BW had no significant effects on DFI or on the main endocrine indicators during lactation. BFT showed stronger associations with DFI (r = -0.47; P < 0.01) and leptin (r = 0.58; P < 0.001) than BW. Partial correlation analyses indicated that the DFI-leptin and DFI-ghrelin associations remained significant after adjustment for BFT, but not after adjustment for BW. Regression models confirmed a greater predictive capacity of BFT than BW for DFI during lactation. These results indicate that BFT is a physiologically more informative indicator than BW for assessing metabolic status and endocrine regulation of appetite during the gestation-lactation transition in primiparous gilts.