| Feed requirement estimates in feeding management of Grass carp(Ctenopharyngodonidellus) havealways been experience-dependent. Feeding too little can lead to growth inhibition, while excessfeed willincreasecosts and result in water pollution. Establishment of biological energetics modelto explore energy demand of grass carpin different environments can provide theoretical basis for accurate feeding. This paper discusses the growth characteristic of grass carp at different water temperature and different growth stages. Fish-Pr FEQ programwas applied to establish energy demand and pollution emission modelfor grass carp. The results are as follows:Trialone: Body composition, growth, mineral absorptionand antioxidant properties were studied in juvenile grass carp(average 55.4g) reared at four temperature series(22°C, 26°C, 30°C and 33°C). The results showed that fish chemical composition and energy content were significantly affected by water temperature(P<0.05) and that moisture and protein content were highest at 22°C.The moisture, protein and energy content of grass carp decreased significantly with the increasing temperature. Temperature did significantly affect the final body weight(FBW), weight gain(WG), special growth weight(SGR), the thermal-unit growth coefficient(TGC) and feed conversion ratio(FCR) of grass carp(P<0.05).The optimal growth temperature was 30°C.The water temperature did not significantly affect whole body,vertebral and scale Ca(%) and Mg(%) levels of grass carp(P>0.05) with the max vertebral and scale Ca content observed at 30°C. Temperature significantly(P<0.05) increased the ROS level, serum superoxide dismutase(SOD) activity, serum catalase(CAT) activity and Glutathione peroxidase(GSH-Px) activity. Total antioxidant capacity(T-AOC) was affected by the temperature significantly(P<0.05) and peaked at 30°C.The conclusion is that 30 ° C is optimal temperature for grass carp in growth and mineral deposition.Trialtwo: The present study aimed to study characteristics of growth pattern, biochemical composition, digestibility and mineral utilization of grass carp atdifferent growth stages and provide sufficient data for constructionof grass carp growth and feed consumption model. The initial weightof five fish groups were 2.1±0.0g,31.3±1.0g,71.1±1.1g,222.0±8.2g and 554.0±18.4g, respectively. After eight weeks, growth performance, apparent digestibility, biochemical composition, and mineral of whole body, vertebra and scale were determined. The results showed that the growth rates of grass carp increased firstly and then decreased with the body weight gain. The grass carp growth could be divided into four stages according to the thermal-unit growth coefficient(TGC). The body moisture, crude protein, crude lipid increased and energy content increased significantly(P<0.05) with the body weight gain. Feed efficiency(FE) decreased with the body weight gain significantly(P<0.05). The apparent digestibility of dry matter(ADCd), protein(ADCp), energy(ADCe) and phosphorus(ADCpi) increased significantly(P<0.05)with the body weight gain. The contents of Ca and P in whole body, vertebra and scale increased significantly(P<0.05).There were no significant differences(P>0.05)among each group in Ca/P of whole body and vertebra with the body weight gain. The content of Mg in whole body and vertebra increased with the body weight gain(P<0.05), but there was no significant difference in scale(P>0.05). In conclusion, according to TGC Growth model, grass growth firstlyincreased and then decreased; With the increasing of body weight, Ca and P content of grass carp kept increasing while the ratio of Ca/P maintained stable during the different growth stages.Trail three: Growth model,feed requirement model and waste output model for commercial grass carp farmingweredeveloped using Fish-Pr FEQ bioenergetics factorial approach with the integration of data from our trials and the published scientific literature. Calculating the observed and predicted growth minimum residual sum of squares(RSS)was used to choose the best growth model. Different growth models were compared to devidethe growth trajectory intothree different production stages(nursery, 0.5–25g BW; pre-growout, 25–750g BW; and growout, >750 g BW) based on data from thecommercial grass carp farm in Hua Zhong agriculture university. Feed requirement was estimated based on digestible energy requirement(DEreq), calculated from the expected energy gain(recovered energy, RE), and estimates of energy losses associated with basal metabolism(He E), heat increment of feeding(Hi E), and urinary and branchial excretion(UE + ZE). All data for estimationby compiling and analyzing was from published literatures. The waste outputs were estimated using nutrient mass balance approach. Feed requirement model simulations were compared with the results from a growth trial carried out under controlled conditions. The modified TGC models produced a better fit forthe growth trajectory of the fish on the commercial farm across production stages compared with other growth models(SGR, DGC, linear).The digestible requirement demand energy as follow:DE=RE[6.13×BWpred-6.13×BWinitial]+He E[(-30.3+2.4T×BWaverage)×0.8]+Hi E[0.45×(RE+He E)]+(UE+ZE)[0.058×(RE+He E+Hi E)].In terms of feeding strategies,we estimatethat if feeds with crude protein content of respectively 40%, 30% and 28%are usedto feed nursery, pre-grownout and grownout from 0.5g to 2500 g, the yields will be 1000 kgwith the grass digestible energy demand about 2.1 × 108 k J, feed demand 15100 kg, total solid waste emissions 344 kg, solid nitrogen emissions 1.3kg, solid phosphorus emissions 0.65 kg, dissolved nitrogen emissions 2.7kg, dissolved phosphorus emissions 0.21 kg.Drawing from the above results, we can conclude that the use of Fish-Pr FEQ feeding management program is a more appropriate method for grass carp farmingprocess. |
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