Effects of cooling temperature stress on hematology and serum chemistry values of Cyprinus carpio

A total of 85 interspecific hybrid F₂ (Cyprinus carpiovar. wuyuanensis×Cyprinus pellegrini pellegrini) were cooled to specific temperatures and held at those temperatures over a maximum of 4 days in a water-recycled and temperature-controlled aquarium inside. As a result, the blood homeostasis of experimental fish changed violently as acute temperature changed from 16 ℃ to 10 ℃ and 4 ℃ at a rate of 1 ℃·h^-1 according to the data we collected. Whole blood pH, also called extracellular pH (pHe) were very sensitive to temperature changes, where the re was a significant difference between 10 ℃ (7.41) and 16 ℃ (7.17) (P <0.01), compared to other values of hematology and serum chemistry. When the water temperature was continually decreased to an extreme temperature of 4℃, the content of Na⁺ of serum decreased remarkably in comparison with that of 10 ℃ and 16 ℃, which was 85.2 mmol·L^-1, 113.3 mmol·L^-1 and 118.7 mmol·L^-1, respectively. The values of hematology and serum chemistry also altered in gentle temperature changes of (10±2) ℃ and (4±2) ℃. Most values of serum chemistry and pH changed significantly, whereas the values of blood plasma changed slightly. pH was up slowly in 4 days at (10±2) ℃ and down slowly in 3 days at (4±2) ℃. A variety of values of serum chemistry changed remarkably both at (10±2) ℃ and (10±2) ℃, but the values of TP, TG and ALB only changed significantly at (4±2) ℃. These results distinguished at least two mechanisms involved in cold-induced stress in hybrid F₂. Cold-induced pH changes resulted in other values altered. What's more, pH correlated negatively with water temperature above 10 ℃, and the content of Na+. We also found that gentle te mperature changes will be physiologically compensated for on day one at (10±2) ℃ and on day 2 at (4±2) ℃ in hybrid F₂.