EFFECT OF RATION LEVEL ON GROWTH, NITROGENOUS EXCRETION AND ENERGY BUDGET IN JUVENILE SOFT-SHELLED TURTLE, PELODISCU S SINENSIS

The 56-day growth trial was conducted at 30 e to investigate the effect of ration level on growth, nitrogenous excretion and energy budget in juvenile sof- t shelled turtle(Pelodiscus sinensis). Juvenile turtles(28166) 53137g) were fed commercial diet (Shenzhen Xinguang Feed company) at five different levels ranging from starvation to ad libitum twice daily. The results showed that specific growth rate(SGR) of wet weight(SGRw), dry matter(SGRdr), protein(SGRp) and energy(SGRe) was affected signif- icantly(P<0101)by ration level. Regression analysis showed that the SGR increased quadraticly with increasing ration.The relationship between specificgrowth rate and ration level(Rl) could be expressed as the equation bellow: SGRw=- 110473+ 017134R- 010512Rl2 (r2= 018314, n= 25, P<0101) SGRdr=- 118779+ 110795Rl- 010832Rl2 (r2= 019064, n= 25, P<0101) SGRp=- 119134+ 111460Rl- 010943Rl2 (r2= 019122, n= 25, P<0101) SGRe=- 215872+ 114014Rl+ 011105Rl2 (r2= 018844, n= 25, P<0101) Feed efficiency in wet weight, protein and energy was highest at 2% ration, which were 36131%, 21147% and 28110% respec- tively.The effects of ration level on ammonia, urea nitrogenous excretion and the proportion of ammonia excretion to total nitrogen excretion were significant (P<0101).The urea and total nitrogenous excretion rate increased with increasing ration, and ranged 8124) 29156(Lmol/g#d) and 18181%) 65187% (Lmol/g#d) from starvation to ad libitum, respectively. Ammonia excretion rate and the proportion of ammonia excretion to total nitrogen excretion at starvation were higher than that of 1% and ranged 9144) 36131(L mol/g#d) and 44150%) 55109%, respectively. Regression analysis showed that the relationship between nitro- gen excretion(L mol/g#d) and protein intake rate(PL) (%body weight per day) could be expressed as: G-N= 316592+ 4911775PL (n= 20,r2= 018716) NH3-N=- 111239+ 2915939PL (n= 20,r2= 018964) U-N= 417831+ 1915836PL (n= 20,r2= 016574) where theG-N, NH3-N and U-N indicategeneral nitrogen, ammonia and urea excretion rate respectively.The proportions of energy intake allocated to various components of the energy budget were significantly affected by ration(P<0101).The proportion of metabolic energy to food energy was highest at 1% ration level which was 86122% and lowest at 2% which was 63154%. the proportion of growth changes was highest at 2% ration level which was 28110%. The energy budget equation for the starvation group could be expressed as: 100C= 6184F+ 2164U+ 72112R+ 17176G where C, F.U, R and G is,, The results showed that the nitrogenous excretion rate increased with increasing ration linearly, while conversion efficiency of en- ergy was highest at lower ration level(2%). In conclusion, the best ration level for juvenile sof- t shelled turtle culture is 4% be- cause the turtle has higher specific growth rate, conversion efficiency and relatively lower nitrogen excretion rate.