| Optimum protein and energy levels, feeding levels and phosphorus requirements and utilization of plant protein source of juvenile Chinese sucker were determined in the present study. The results obtained can be briefly summarized as follows:1. A growth experiment was conducted to investigate effect of dietary protein to energy ratios on growth and body composition of juvenile Myxocyprinus asiaticus (initial mean weight:10.04±0.53 g, mean±S.D.). Nine practical diets were formulated to contain three protein levels (340,390 and 440 g Kg-1), each with three lipid levels (60, 100 and 140 g Kg-1), in order to produce a range of P/E ratios (from 22.4 to 32.8 mg protein kJ-1). Each diet was randomly assigned to triplicate groups of 20 fish in 400-L indoors flow-through circular fibreglass tanks provided with sand-filtered aerated freshwater. The results showed that the growth was significantly affected by dietary P/E ratio (P<0.05). Fish fed the diets with 440 g Kg-1 protein (100 and 140 g Kg-1 lipid, P/E ratio of 31.43 and 29.22 mg protein kJ-1) had the highest specific growth rates (SGR) (2.16 and 2.27% day-1, respectively). However, fish fed the diet with 390 g Kg-1 protein and 140 g Kg-1 lipid showed comparable growth (2.01% day-1), and had higher protein efficiency ratio (PER), protein productive value (PPV) and energy retention (ER) than other groups (P<0.05). No significant differences in survival were found among dietary treatments. Carcass lipid content was positively correlated with dietary lipid level, but irrespective of protein level and inversely correlated with carcass moisture content. Carcass protein contents increased with increasing dietary lipid at each protein level. The white muscle and liver composition showed that lipid increased with increasing dietary lipid level (P<0.05). Dietary protein concentrations had significant effect on condition factor (CF), hepatosomatic index (HSI) and viscerosomatic index (VSI) (P<0.05). However, Dietary lipid concentrations had no significant effect on CF, HSI (P>0.05). Based on these observations,440 g Kg-1 protein with lipid from 100 to 140 g Kg-1 (P/E ratio of 29.22 to 31.43 mg protein kJ-1) seemed to meet minimum requirement for optimal growth and feed utilization, and lipid could cause protein-sparing effect in diets for juvenile Chinese sucker.2. A growth trial was conducted to estimate the optimum requirement of dietary available phosphorus (P) for Chinese sucker juveniles. Triplicate groups of juveniles Chinese sucker (initial mean weight:1.77±0.02 g, mean±S.D.) were fed diets containing graded levels (3.1,5.3,7.5,9.6 and 11.8 g kg-1) of available phosphorus. The basal diet (diet 1), containing 3.1 g kg-1 available P, was supplemented with graded levels of monocalcium phosphate (MCP) to formulate four experimental diets. The fish were fed twice daily (08:00 h and 17:00 h) to satiation for 8 weeks. During the experimental period, the water temperature fluctuated from 27.5 to 30.5℃and dissolved oxygen was more than 6 mg l-1. The specific growth rate (SGR), protein efficiency ratio (PER) were all significantly increased by dietary available phosphorus up to 7.5 g kg-1 (P<0.05) and then leveled off beyond this level. Feed conversion ratio (FCR) significantly decreased with dietary available phosphorus level up to 7.5 g kg-1 (P<0.05). Dietary treatments did not significantly affect feed intake (FI) (P>0.05). Efficiency of phosphorus (P) utilization significantly decreased with dietary available phosphorus level (P<0.05). Body composition analysis showed that the whole-body lipid, ash, calcium, phosphorus, magnesium(Mg), zinc(Zn), copper(Cu) contents were all significantly affected by dietary available P concentration (P<0.05), however, no significance were found Manganese(Mn) concentration and calcium/phosphorus (Ca/P) ratios in whole-body among all the treatments (P>0.05). Dietary phosphorus levels also significantly affected the mineralization of vertebrae and scale (P<0.05), and Ca/P ratios in scale were not influenced by dietary P supplementation, while vertebrae Ca/P ratio decreased with dietary available P levels (P<0.05) (quadratic effect, P<0.001). Signs of phosphorus deficiency were characterized by poor growth, slightly reduced mineralization and an increase in body lipid content. The blood chemistry analysis showed that dietary available P had distinct effects on enzyme activities of alkaline phosphatase (ALP), as well as contents of triacyglycerol (TG) and total cholesterol (T-CHO) (P<0.05). Broken-line analysis based on weight gain (WG) indicated the minimum available phosphorus requirement for the optimal growth of juvenile Chinese sucker was 7.4 g kg-1. Based on the phosphorus content in whole body, vertebrae or scale indicated that the requirements were 8.3,8.8 and 8.6 g kg-1, respectively.3. Building a reliable database on apparent digestibility of protein sources is critical for accurate feed formulation and reduction of aquaculture wastes. Apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein, crude lipid, gross energy, phosphorus and amino acids for white fish meal (WFM), brown fish meal (native) (BFM), fermented soybean meal (FSBM), extruded soybean meal (ESBM), soybean meal (SBM), cottonseed meal (CM) and rapeseed meal (RM) were determined for Chinese sucker (Myxocyprinus asiaticus) (18.05±0.27g) using a reference diet (RF) and test diets (70% RF diet plus 30% of tested feedstuff) containing 0.5% chromic oxide as an inert marker. WFM had the highest apparent digestibility coefficient for DM (74.5%). For plant products, the ADCs of DM ranged from 54.3 to 71.6%. Protein digestion by Chinese sucker of WFM, BFM, FSBM and ESBM was significantly higher than CM and RM, ranging from 72.8 to 92.3% for plant products, and 90.3 to 91.2% for animal feedstuffs. Lipids from both animal and plant feedstuffs were highly digested by Chinese sucker, ranging from 89.8 to 94.9%. The highest digestibility coefficient of energy was registered for WFM, followed by BFM; and the lowest digestibility coefficient of energy was recorded for CM (P<0.05). The Chinese sucker did utilize dietary phosphorus from the animal feedstuffs (FSBM and ESBM) more efficiently than from plant feedstuffs (SBM, CM and RM), with values ranging from 58.8 to 61.4% and 25.8-56.0%, respectively. Amino acid availability reflected protein digestibility, except for ESBM, for which the availability of some amino acids was lower, possibly because of protein denaturation during processing. Based on the current findings, FSBM and ESBM could be considered as good potential substitutes for FM in diets for Chinese sucker.4. The study was designed to study the growth performance of the Chinese sucker, Myxocyprinus asiaticus in response to the replacement of fish meal with Fermented Soybean meal (FSBM) in its diet. Seven isonitrogenous and isolipidic diets were formulated with 0,15,25,35,45,55 or 65% replacement of fish meal with FSBM on a protein basis. Each diet was fed to three replicate groups of fish with an initial weight 4.59±0.2 g for eight weeks. Weight growth (WG) and Specific growth rate (SGR) was significantly lower when FSBM inclusion was 45% or greater, replacing more than 45% fish meal protein. A significant negative relationship was observed between growth response and the level of fish meal protein replacement with FSBM protein. Methionine and Lysine content decreased as FSBM inclusion levels increased, consequently compromising growth performance. Feed intake (FI) were unaffected by fish meal replacement levels. The feed conversion ratio (FCR) and the protein efficiency ratio (PER) were highest at the lowest FSBM inclusion level. Experimental diets D-0, D-15, D-25 and D-35 had apparent dry matter digestibility (ADMDs) ranging from 71.17-72.55% and apparent protein digestibility (ADPs) from 89.07-90.08%, while the diets with higher FSBM inclusion (D-45 to D-65) had a significantly lower ADMDs range (69.74-70.26%) and APDs range (88.54-88.86%). It is concluded that FSBM is an acceptable alternative plant protein source that can replace up to 35% of fish meal protein in diets without significant adverse effects on growth, survival, FCR, PER and body composition.5. An 8-week feeding trial was conducted using six test diets to evaluate the effects of supplementation of crystalline or coated lysine (Lys) and/or methionine (Met) on growth performance and feed utilization of the Chinese sucker, Myxocyprinus asiaticus. Test diets were fed to triplicate groups of Chinese sucker (about 3.3 g) two times a day. Five iso-nitrogenous and iso-caloric diets based on fermented soybean meanl (FSBM) were prepared by either not supplementing with lysine and methionine (NLM), or supplementing with both crystalline Lys and Met (LM), with coated Lys (CL), with coated Met (CM), or with both coated Lys and Met (CLM). The control diet (FM) was formulated to contain 65% fish meal as the sole animal protein source without amino acid (AA) supplementation. The Chinese sucker juveniles fed the CL, CM and CLM diets had higher weight gain (WG) and protein efficiency ratio (PER) compared to Chinese sucker fed the NLM diet (P<0.05). The Chinese sucker juveniles fed the CLM diet showed significantly higher growth performance than those fed the LM diet (P< 0.05). Feed intake (FI) and survival among all groups at the end of the experiment were not significantly affected by the dietary treatments. The whole body, muscle proximate, total amino acid composition showed few differences among the groups. The Chinese sucker juveniles fed the CLM diet showed significantly higher CF, HSI and VSI than those fed the NLM diet. This study indicated that the supplementation of coated lysine and methionine was effective in improving the nutritive value of FSBM-based diets deficient in methionine and lysine for juvenile Chinese sucker.6. An experiment was conducted to determine effects of feeding levels on growth performance, feed utilization, nutrient deposition, body composition, and apparent digestibility coefficients (ADCs) of nutrients for juvenile Chinese sucker (initial weight, 11.77±0.22 g). Chinese sucker were fed a practical diet from 0 (starvation) to 4.0% (at 0.5% increments) body weight per day (bw d-1) for 8 weeks. The results showed that growth performance, feed utilization, nutrient deposition, body composition, and ADCs of dry matter, protein, and energy were significantly (P<0.05) affected by feeding levels. Survival was the lowest for the starvation group. Final mean body weight, Growth rate, thermal-unit growth coefficient (TGC) increased with feeding rate from 0 to 3.0% bw d-1 (P<0.05) and showed no significant differences above the level (P>0.05). Feed conversion rate was significantly lower at a feeding level of 2.5% bw d-1 than above and below the level (P<0.05). Protein efficiency ratio was markedly highest at the 2.5% bw d"1 ration level (P<0.05). Fish fed at the feeding level (1.0% bw d-1), which represented a maintenance ration (energy gain was less than 2.27 kJ fish-1 day-1), showed positive protein deposition but negative lipid deposition. This indicates that fish fed a maintenance ration mobilize body lipid reserve to support protein deposition. Lipid contents of whole body, muscle, and liver increased with increasing feeding rates from 0.5 to 3.0% bw d-1 and showed no significant differences above the level (P>0.05). Protein contents of whole-body composition increased with feeding rate from 0.5 to 3.0% bw/d (P<0.05) and showed no significant differences above the level (P>0.05), whereas muscle, and liver remained relatively stable with the different ration amount with the exception of fish fed a ration of 0.5% bw d-1, at which Chinese sucker possessed significantly lower body protein concentration (P<0.05). ADCs of dry matter, protein, and energy decreased with increasing feeding levels from 0.5 to 3.0% bw d-1 and then remained relatively constant over the level. Based on the broken-line regression analysis using WG data, the optimum and maintenance feeding levels for Chinese sucker were 3.10% bw d-1 and 0.45% bw d-1, respectively... |
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