The study looked at fish that were heated up to stressful temperatures and found they grew less, had blood and gut problems, and showed lower levels of the growth hormone gene IGF‑1. Adding probiotics to the water or spirulina to the feed helped the fish stay healthier, grow better, and restored IGF‑1 gene activity. The work is done in a fish model, not humans.

Climate change-induced high-water temperature is continuously posing several detrimental effects on physiology and production of aquaculture species. To overcome the constraints of rising water temperature, this study aimed to evaluate whether probiotics and Spirulina platensis supplementation mitigate thermal stress-induced physiological impairment in Labeo rohita. Fingerlings were reared at four different groups such as 30 °C as ambient temperature, 36 °C as elevated temperature, and two supplemented groups as 36 °C + Probiotics (1 ml/L in water) and 36 °C + Spirulina platensis (50 g/kg in feed) for 42 days. At the end of the exposure, growth parameters such as weight gain and specific growth rates were significantly lower in elevated temperature with higher feed conversion ratio. Blood parameters such as glucose and hemoglobin were also found lower along with higher incidences of erythrocyte cellular and nuclear anomalies and significantly higher histoarchitectural abnormalities in intestine at 36 °C. Moreover, elevated temperature also exerted growth inhibition, oxidative stress and suppressed immunity by downregulation in the expression of growth-(gh, igf-1 and igf-2), antioxidants (SOD and GPX) and immune (IgM, IL-1β, LyZ-C and TNF-α) related genes at 36 °C. However, incorporation of either probiotics or Spirulina platensis showed promising effects in fish reared in elevated temperature and significantly improved growth, blood and histological anomalies of gut, oxidative stress, heat-shock proteins and immune markers compared to non-supplemented elevated temperature group. Therefore, this study suggests first evidence in Labeo rohita incorporating probiotics or Spirulina platensis in combating high temperature-induced growth hindrance, detrimental physiological effects, and gene-level restoration under heat stress for sustained aquaculture production.