ABSTRACT

Background and Aim: Metabolic adaptation during the transition period is a major determinant of reproductive performance in dairy cows. Insulin-like growth factor-1 (IGF-1), a key regulator of the somatotropic axis, links nutritional status with endocrine function and postpartum reproductive recovery. Fermented potato protein (FPP), a value-added agro-industrial by-product, has improved protein digestibility and may contain bioactive compounds that modulate metabolic pathways. However, its effects on endocrine regulation and reproductive performance in tropical crossbred dairy cattle remain poorly understood. This study aimed to evaluate the effects of FPP supplementation on serum IGF-1 concentrations, skeletal muscle IGF-1 mRNA expression, and the interval from calving to first postpartum estrus.

Materials and Methods: Two experiments were conducted. In Experiment 1, ten clinically healthy Bos taurus × Bos indicus crossbred dairy heifers were randomly assigned to either a control group or an FPP-supplemented group (30 g/head/day; n = 5/group) for 45 days. Serum IGF-1 concentrations were quantified using enzyme-linked immunosorbent assay, whereas skeletal muscle IGF-1 mRNA expression was determined by quantitative real-time polymerase chain reaction. In Experiment 2, twenty-four transition dairy cows (parity 1-2; n = 12/group) received either the basal diet or FPP supplementation from 3 weeks prepartum to 6 weeks postpartum. The interval from calving to first postpartum estrus was monitored using an automated pedometer and confirmed by transrectal ultrasonography.

Results: FPP supplementation significantly increased serum IGF-1 concentrations on day 30 (17.97 ± 4.93 vs. 7.82 ± 0.87 ng/mL; p = 0.016) and day 45 (18.45 ± 4.13 vs. 7.72 ± 0.75 ng/mL; p = 0.016), whereas no significant differences were observed on days 0 and 15 (p > 0.05). Skeletal muscle IGF-1 mRNA expression did not differ between groups (0.82 ± 0.07 vs. 0.84 ± 0.14; p = 0.90). Cows supplemented with FPP exhibited a numerically shorter interval from calving to first postpartum estrus than controls (43.83 ± 2.40 vs. 50.00 ± 2.06 days), although the difference was not statistically significant (p = 0.06).

Conclusion: FPP supplementation increased circulating IGF-1 concentrations without altering skeletal muscle IGF-1 mRNA expression, suggesting that its biological effects are mediated primarily by systemic endocrine regulation rather than by local tissue-specific mechanisms. Although improvement in postpartum reproductive recovery was not statistically significant, the concurrent increase in circulating IGF-1 and shorter estrus interval indicate that FPP may represent a sustainable nutritional strategy for improving metabolic adaptation in tropical dairy cattle. Larger studies are warranted to confirm its reproductive benefits and establish its role in precision nutritional management.

Keywords: agro-industrial by-product, dairy cattle, endocrine regulation, fermented potato protein, insulin-like growth factor-1, postpartum estrus, reproductive performance, somatotropic axis.