Effects of dietary phosphorus on growth, body composition, and blood chemistry of juvenile taimen Hucho taimen

To determine the optimum P requirements of taimen (Hucho taimen), the present study investigated the effects of diets supplemented with different levels of inorganic P (NaH2PO4) on growth, proximate composition, blood chemistry, and mineralization in juvenile taimen. Triplicate groups of fish (mean initial weight 15.39 ± 0.28 g) were fed, until satiation, with different diets containing graded levels of digestible P (0.22, 0.40, 0.55, 0.74, 0.90, and 1.07%), for 84 days. Weight gain, feed conversion ratio, and protein retention were significantly (P 0.05). With increasing dietary P levels, P retention and whole-body lipid content decreased from 75.41 ± 7.06 to 36.41 ± 3.30% and from 3.23 ± 0.13 to 2.74 ± 0.25%, respectively, whereas vertebrae ash and plasma P content increased from 43.68 ± 0.23 to 52.09 ± 0.28% and from 2.18 ± 0.14 to 3.98 ± 0.23 mmol L−1, respectively. Using a broken-line regression model that incorporated measurements of P digestibility, feed efficiency, and normal whole-body and vertebrae P content, the dietary requirement of digestible P was determined to be approximately 0.5% for taimen.