Study On Calcium And Phosphorus Nutritional Physiology Of Bullfrog Rana(Lithobates) Catesbeiana

A feeding trial was conducted to evaluate the effects of dietary calcium(Ca), phosphorus(P) and their interaction on growth, digestibility, body composition, bone mineralization and some blood parameters in juvenile bullfrog Rana(Lithobates) catesbeiana. Nine isonitrogenous(40% crude protein) and isoenergetic(7% crude lipid) diets, containing three graded levels of Ca(calcium lactate) supplementation level(0%, 0.4% and 0.8%) for each of three levels of P(Na H2PO4) supplementation level(0%, 0.4% and 0.8%), were fed to juvenile bullfrog(12.78±0.35 g). Prior to the trial, bullfrogs were fed with the basal diet(0.7% total Ca and 0.8% total P) for 2 weeks. Results of the present study were presented as follows:1. Effect of dietary Ca and P levels on growth and body composition of bullfrogAfter 60 days, all bullfrogs normally grow without morphological deformities. Weight gain(WG), ranging from 614.14% to 680.16% among the treatments, a significant increase in growth was observed in bullfrog fed diets with 0.8% Ca supplementation regardless of dietary P levels. Our results showed that specific growth rate(SGR) and feeding rate(FR) were significantly affected by dietary Ca, FR also was significantly affected by dietary P(P<0.05), but higher dietary P had a negative impact on feed efficiency(FE). Hepatosomatic index(HSI) was significantly increased in fed diets with 0.4% Ca, HIS and viserosomatic index(VSI) were significantly affected by the interaction between Ca and P. No significant difference among all treatments in crude protein of body composition, A significant reduction occurred in crude lipid of body composition and serum triglyceride(TG) contents with the increasing of dietary P(P<0.05). In conclusion, the current study indicated that higher dietary Ca is essential for maintaining normal growth.2. Effect of dietary Ca and P levels on bone mineralization and some blood parameters of bullfrogSerum P level was retained relative balance, Alkaline phosphatase(AKP) activity reduced with the increasing of dietary P(P<0.05). Serum Ca was significantly increased with 0.8% Ca supplementation and affected by the interaction between Ca and P. Crude ash contents in vertebrae and leg bone were significantly affected by the addition of dietary Ca and P, the contents of Ca in vertebrae and P in leg bone was significantly increased with 0.8% Ca supplementation, Ca and P contents in vertebrae was increased with the elevation of dietary P levels(P<0.05). The lower Ca and P contents in vertebrae occurred in fed diet with 0.8% Ca supplementation without P supplementation. Higher leg bone breaking strength and breaking pressure occurred on 0.8% Ca supplementation or 0.4-0.8% P supplementation(P<0.05), the diameter of leg bone changed regardless of dietary Ca or P level or the interaction. Sodium(Na) and Potassium(K) contents in muscle, vertebrae and leg bone significantly decreased with the increasing of dietary Ca contents, on the contrary, dietary P significantly improved depression of Na and K contents. Magnesium(Mg) content of muscle significantly decreased on 0.8% Ca supplementation level, Mg, manganese(Mn) and zinc(Zn) contents in whole-body significantly increased with the elevation of dietary P levels, Mn content was affected by the interaction(P<0.05). The deposition of Mg, Mn, Zn, Iron(Fe) and copper(Cu) in vertebrae and Fe and Zn in leg bone was inhibited by dietary Ca supplementation, however, dietary P supplementation promoted deposition of these elements(P<0.05). Mg and above trace elements contents were affected by the interaction between Ca and P. In a word, crude ash, Ca and P of vertebrae and leg bone increased with the elevation of dietary Ca or P, dietary Ca inhibited cation absorption(K, Na, Mg, Fe, Cu, Mn and Zn), while dietary P improved the depression.3. Apparent digestibility coefficients of nutrients in different Ca and P level diets of bullfrogTwo-way ANOVA showed that apparent digestibility coefficients(ADC) of dry material significantly decreased with the increasing of dietary Ca or P. ADC of dietary crude protein, crude lipid and P significantly decreased at 0.8% Ca supplementation level, while ADC of Ca showed a rising trend with dietary Ca supplementation, then lowed, higher ADC of Ca at 0.4% dietary Ca supplementation(P<0.05). ADC of dietary crude protein, crude lipid and P significantly increased at 0.4% and 0.8% P supplementation, however, the lower ADC of P occurred on higher P supplementation level(P<0.05). ADC of dry material, crude protein and P was affected by the interaction between Ca and P. In summary, higher dietary Ca level inhabited nutrients absorption, on the contrary, higher dietary P level promoted the bad inpact of absorption(except P). The basal diet contained available Ca and P contents were 0.44% and 0.57%, respectively. Apparent digestibility of Ca in calcium lactate and P in Na H2PO4 was calculated to be 70% and 95%, respectively.The results of present study indicated that the diet contained 1.5% total Ca(0.86-1.01% available Ca) and 1.2% total P(0.83-0.95% available P) was optimal for bullfrog.