Nutritional assessment of Australian canola meals. I. Evaluation of canola oil extraction method and meal processing conditions on the digestible value of canola meals fed to the red seabream (Pagrus auratus, Paulin)

This study assessed the nutrient and energy digestibility of a variety of canola protein products that were produced by processing canola meal under different conditions, using the red seabream, Pagrus auratus. The test canola protein products included solvent‐extracted canola meal, expeller‐extracted canola meal alone or subjected to one of two different heat treatments (120 or 150°C for 30 min), and expeller meal further processed to produce a canola protein concentrate (CPC). Solvent‐extracted soybean meal was also included in the study as a reference ingredient. Daily feed intake and blood thyroid hormone levels over the experimental period were also examined. The total digestible protein content of the expeller‐ and solvent‐extracted canola meals was 356 and 358 g per kg dry matter (g kg DM^?1) respectively. The total digestible energy content of the expeller‐ and solvent‐extracted canola meals was 14.23 and 8.60 MJ kg^?1 respectively. The organic matter digestibilities of the solvent‐extracted canola meal were poorer than noted for the expeller‐ and solvent‐extracted soybean meal. Notably, the two sources of canola meals used in this study (solvent and expeller meals) did not cause problems with declining feed intakes or changes to blood levels of thyroid hormones when included in the diets of the fish at a 30% level, and the diets were fed over a 3‐week period. The preparation of a CPC resulted in gains in total digestible energy, but a reduction in the amount of total digestible protein, relative to the expeller canola meal from which it was produced. However, the protein concentrating process marginally reduced the relative digestible value of the protein content. Heating expeller meal at 120 or 150°C for 30 min resulted in progressive reductions of all nutrient and energy digestibilities.     

A comparison of the digestibility of lupin (Lupinus sp.) kernel meals as dietary protein resources when fed to either, rainbow trout, Oncorhynchus mykiss or red seabream, Pagrus auratus

The nutritional value of the kernel meals of three species of lupin (Lupinus albus, L. angustifolius and L. luteus) was compared against each other and solvent extracted soya bean meal and wheat gluten, when fed to either rainbow trout or red seabream. The digestible nutrient and energy values were determined for each ingredient, based on the diet substitution digestibility method. Each test ingredient was included in test diets at 300 g kg^?1. As different faecal collection methods were used on each species, only ingredient comparisons within each fish species study are valid. Protein digestibility for all lupin kernel meals was significantly better than for soya bean meal when fed to red seabream, although only numerically so when fed to rainbow trout. The highest protein digestibility in both fish species was that from the wheat gluten (100.0% for both rainbow trout and red seabream). Energy digestibility for each of the lupin kernel meals (range 62.4%–64.9% in rainbow trout and 60.9%–69.5% in red seabream) was less than that obtained from soya bean meal (75.1% and 81.0% for rainbow trout and red seabream, respectively). However, the higher gross energy content of the lupin kernel meals still resulted in both L. albus and L. luteus providing equivalent levels of digestible energy as that of soya bean meal. Organic matter digestibility was generally poorer for each of the lupin kernel meals relative to that for the soya bean meal and particularly compared with the wheat gluten. Phosphorus digestibility was significantly better in all lupin kernel meals than that from both the soya bean meal and wheat gluten. Highest phosphorus digestibility was that obtained from L. albus kernel meal (100.0% for both rainbow trout and red seabream) although notably the phosphorus digestibility of all lupin kernel meals when fed to rainbow trout was determined at 100%. Similarly the digestibility of phosphorus from lupin kernel meals fed to red seabream was also very high. This study supported the good nutritional value to both rainbow trout and red seabream of kernel meals of all three species of lupin, although the digestible nutrient attributes of kernel meal from L. luteus were particularly favourable.     

Evaluation of fisheries by-catch and by-product meals in diets for red drum Sciaenops ocellatus L.

This study evaluated various by‐catch and by‐product meals of marine origin with red drum (Sciaenops ocellatus L.). Four different kinds of by‐catch or by‐product meals [shrimp by‐catch meal from shrimp trawling, Pacific white shrimp (Litopenaeus vannamei (Boone)) processing waste meal, red salmon (Oncorhynchus nerka (Walbaum)) head meal, and Pacific whiting (Merluccius productus (Ayres)) meal] were substituted for Special Select? menhaden fish meal at 33% or 67% of crude protein in diets formulated to contain 40% crude protein, 12% lipid, and 14.6 kJ digestible energy g^?1. Each of these diets and three additional diets consisting of shrimp processing waste meal formulated on a digestible‐protein basis and two Pacific whiting diets containing reduced levels of ash were also evaluated in two 6‐week feeding trials with juvenile red drum (initial weight of 4–5 and 1–2 g fish^?1 in trials 1 and 2). Red drum fed by‐catch meal at either level of substitution performed as well as fish fed the control diet; whereas, fish fed shrimp processing waste meal diets had significantly (P≤0.05) reduced weight gain and feed efficiency ratio values compared with the controls, even when fed on a digestible‐protein basis. The diets containing Pacific whiting at either levels of substitution and regardless of ash level supported similar performance of red drum as those fed the control diet. Fish fed the red salmon head meal diet fared poorly, probably owing to an excessive amount of lipid in the diet that became rancid. Overall, by‐catch meal associated with shrimp trawling and Pacific whiting appear to be suitable protein feedstuffs for red drum.     

A comparison of the growth performance of rainbow trout (Oncorhynchus mykiss) when fed soybean,narrow‐leaf or yellow lupin meals in extruded diets

This study compared the effect of increasing dietary inclusion of soybean, narrow‐leaf lupin or yellow lupin kernel meals when fed to rainbow trout. Each meal was formulated into a test diet to create a series of inclusion levels of 0, 100, 200, 300 and 400 g kg^?1. Each diet was formulated to the same digestible protein and energy specifications. The diets were fed to apparent satiety to 30.0 ± 0.71 g rainbow trout for 28 days. After this period, fish in the reference (0 g kg^?1) treatment attained a weight of 93.2 g. Growth of the fish among the treatments was observed to be improved by the addition of either variety of lupin meal. In contrast, growth of fish fed the soybean meal was equivalent to that of the 0 g kg^?1 fish meal reference, but was poorer at the 400 g kg^?1 inclusion level. Feed intake with the lupin meals was marginally improved with lupin inclusion, but at the higher soybean meal inclusions, feed intake was reduced relative to the fish meal reference diet. The inclusion of the different grains also had significant effects on the physical properties of the pellets.     

Apparent digestibility of Asian carp‐ and common carp‐derived fish meals in feeds for hybrid striped bass Morone saxatilis ♀ × M. chrysops ♂ and rainbow trout Oncorhynchus mykiss

Apparent digestibility coefficients (ADCs) of nutrients (crude protein, amino acids, crude lipid, fatty acids, and minerals) were determined for fish meals derived from menhaden, Asian carp (combination of silver and bighead carps), and common carp in feeds for hybrid striped bass and rainbow trout. Extruded test diets were formulated to contain a 70 : 30 mixture of reference diet and test ingredient with yttrium oxide (1 g kg^?1) serving as the inert marker. Diets were randomly assigned to triplicate tanks and fish were fed once per day at 2% body weight. Fecal samples were collected by manual stripping. The ADCs were calculated according to standard procedures. The composition and digestibility of Asian carp and common carp meals was broadly similar to menhaden meal. Protein digestibility ranged from 86.5% (Asian carp meal) to 93.1% (common carp meal). Lipid was highly digestible with ADCs >100% for all ingredients. Although the Asian carp meal was less digestible than the other two fish meals, it was still a highly digestible ingredient. Our data suggest that fish meals derived from Asian or common carp would be valuable feedstuffs in diets for hybrid striped bass, rainbow trout, and possibly other cultured fishes.     

Nutritive values of low and high fibre canola meals for shrimp (Penaeus vannamei)

This study was undertaken to determine acceptable dietary concentrations of high-fibre canola meal (CMHF) and low-fibre canola meal (CMLF) for juvenile shrimp, Penaeus vannamei. Four groups of 0.78 g shrimp held in running, 24.0–27.8°C sea water on a 12 h light: 12 h dark cycle were each fed one of seven isonitrogenous (340 g kg^?1 protein) and isoenergetic (18.5 MJ of gross energy kg^?1) diets to satiation four times daily for 56 days. Each of the test canola protein products comprised either 150, 300 or 450 g kg^?1 of the protein in a basal (practical) diet by replacement of one-third, two-thirds or all of the menhaden meal protein. Shrimp that ingested diets in which CMHF and CMLF comprised 450 and 300 g kg^?1 of the protein, respectively, exhibited significant reductions in growth and feed intake relative to those fed the basal diet. Feed and protein utilization were not significantly depressed unless menhaden meal in the basal diet was completely replaced by CMHF or CMLF. In general, percentage survival and final whole-body levels of protein, minerals, and thyroid hormones were not significantly affected by dietary treatment. Terminal whole-body levels of moisture were raised significantly in shrimp fed diets containing the highest levels of CMHF and CMLF. Potassium levels were significantly higher in shrimp fed the diet containing the lowest level of CMLF relative to those fed the basal diet and the diet with the highest level of CMLF. Water stability of the diet pellets was negatively correlated with their levels of CMHF and CMLF. It is concluded that commercial high-fibre canola meal can constitute 300 g kg^?1 of the dietary protein of juvenile shrimp (Penaeus vannamei) without compromising growth, feed intake and feed and protein utilization. However, because of a trend towards reduced shrimp survival at this dietary concentration of canola meal, it is recommended that this protein source not exceed 150 g kg^?1 of the protein in practical juvenile shrimp diets. Fibre-reduced canola meal did not have improved nutritive value for shrimp. However, we postulate that one or more fibre-reduced, and solvent-extracted canola protein products may be cost-effective substitutes for fish meal protein.     

Assessing the implications of variability in the digestible protein and energy value of lupin kernel meals when fed to rainbow trout, Oncorhynchus mykiss

A series of studies were designed to examine the degree of variability in the digestibility of protein and energy from lupin (Lupinus angustifolius) kernel meals when fed to rainbow trout (Oncorhynchus mykiss) and the potential implications of this variability. The digestibility of protein and energy from 10 different varieties of lupin kernel meal was assessed where the test ingredient comprised 30% of each test diet. Digesta was collected using faecal stripping techniques. Digestible protein value ranged from 331 to 508 g/kg DM and digestible energy values ranged from 10.6 to 13.3 MJ/kg DM. To examine the implications of variability in digestible protein and energy value, two lupin kernel meals from the extremes of the protein digestibility range (Lupin-1: AD_N ~ 70% and Lupin-2: AD_N ~ 100%) were chosen for assessment in two growth studies. Soybean meal and a reference diet with fishmeal as the only protein source were also included in the study. In the first growth experiment the test ingredients were included at equal concentrations (40%) in protein-limiting diets (350 g protein/kg DM) and fed at either of two ration levels (restricted and satiety). Diets were formulated on a crude basis so as to place the test variable on the variability in digestible protein value of the diets. In the restricted-fed treatments growth of fish fed the reference diet was highest, but not significantly better than lupin-H. Growth of fish fed the lupin-L diet was significantly poorer than both the reference and lupin-H diets, but not poorer than the soybean diet. The growth responses observed from this experiment clearly showed that the differences in feed intake and/or digestible protein value could be demonstrated in terms of significant differences in growth outcomes. In a second growth study high-nutrient dense extruded diets (400 g protein/kg and 23.5 MJ/kg) were prepared with a more practical level of 25% inclusion of the same test materials. Again the diets were formulated on crude basis so as to place the test variable on the variability in digestible protein and energy value of the diets. Growth of fish restrictively fed the lupin-H diet was highest, but not significantly better than the soybean, reference or lupin-L treatments restrictively fed. Growth of fish satietal fed the soybean diet was significantly poorer than the reference and lupin-H diets, but not compared to the lupin-L diet. The growth responses observed from this experiment showed that the differences in digestible protein and energy value could not be demonstrated in terms of significant differences in growth outcomes, and that feed intake variability and excess nutrient supply masked the effect of this variability; particularly at the satietal feed intake levels.     

Effect of partial and total replacement of fish, shrimp head, and soybean meals with red crab meal Pleuroncodes planipes (Stimpson) on growth of white shrimp Litopenaeus vannamei (Boone)

Red crab meal (RCM), as a potential protein source in diets for juvenile shrimp Litopenaeus vannamei, was evaluated over a 45‐day growth trial under laboratory conditions. Eight experimental diets were tested. The basal diet contained fish (tuna by‐product), shrimp head and soybean (solvent extracted) meals as primary protein sources. Fish or soybean meals were substituted, on an equal‐protein basis, at 33%, 66% and 100% by RCM, whereas shrimp head meal (SHM) was substituted at 100%. A commercial diet was included as a reference. Final weight ranged between 2.23 and 3.36 g and growth rates (GRs) between 0.048 and 0.073 g day⁻¹. Where 66% or 100% of the protein from fish or soybean meals was substituted by RCM, the diets produced significantly higher final weights and GRs than other diets. Regression analysis showed that final weight of shrimp depended significantly on the percentage of substitution, and that the maximum weight gain would be obtained when substituting RCM for 80.2% of fish meal and 81.2% of soybean meal. Feed conversion ratio was below 1.8 for all treatments and there was no apparent relationship with other aspects of the diet. Red crab meal served as a suitable protein source for partial or total replacement of tuna by‐product, soybean and SHMs for cultivated juvenile shrimp L. vannamei.     

Effects of canola meal on physiological and biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (initial body weight 4.16 ± 0.25 g) were fed diets [crude protein 420 g kg^?1; gross energy 18.7 MJ kg^?1 dry matter (DM); crude fat 110 g kg^?1] containing graded levels of either a canola meal (crude protein 350 g kg^?1 DM) supplemented with DL‐methionine as partial fish meal protein. A growth trial was conducted over 16 weeks at a water temperature of 12 ± 1 °C. At the end of the growth trial, in addition to body composition analyses, plasma tri‐iodothyronine (T₃) and thyroxine (T₄), cholesterol and liver fatty acid composition were measured. Replacement of fish meal with canola meal (100–570 g kg^?1 replacement) did not affect on growth performance. At 16th week, plasma cholesterol levels were reduced in fish fed all diets in comparison with 8th week. Plasma T₄ levels were significantly higher in the canola meal‐fed fish sampled after 16 weeks, but no significant differences in T₃ levels were obtained (P > 0.05). Proximate compositions were affected by dietary treatments. The liver fatty acid composition reflected that of the diet with a higher level of polyunsaturated (n‐6) fatty acids in fish fed diet canola meal and a higher content in n‐3/n‐6 ratio in fish fed diet without canola meal. These studies show that canola meal has potential to replace substantial levels of fish meal in diets for carnivorous fish without compromising performance.     

Influence of lupin and rapeseed meals on the integrity of digestive tract and organs in gilthead seabream (Sparus aurata L.) and goldfish (Carassius auratus L.) juveniles

Two rearing trials were conducted to evaluate the effects of dietary lupin (LM) and rapeseed (RM) meals in gilthead seabream (Sparus aurata L.) and goldfish (Carassius auratus L.) juveniles. Each plant meal was incorporated at the rate of 200 g kg^?1 in two distinct diets, which were compared with a fishmeal‐based diet as control. After 1 month, the two plant diets did not influence the whole body growth, but the digestive systems were affected. The splenosomatic index was reduced with two plant meals in goldfish and with RM in seabream. The hepatosomatic index was only reduced in LM‐fed seabream. Cellular characteristics were also affected. The largest liver cells were observed in RM‐fed goldfish suggesting changes in metabolic function. The LM and RM diets stimulated in seabream, especially the reaction in haematopoietic tissues with the proliferation of melano‐macrophages centres, and a tendency for elongated villus height in the anterior intestine thus that possibly compensated for a reduction in digestive function. Such adaptive structural modifications and the absence of degenerative signs allowed concluding that the integrity of the digestive system was maintained in fish fed plant meals.     

Using Near Infrared Reflectance Spectroscopy (NIRS) to predict the protein and energy digestibility of lupin kernel meals when fed to rainbow trout,Oncorhynchus mykiss

This study examined the potential of using near infrared spectroscopy (NIRS) to predict the nutrient composition, energy density and the digestible protein and digestible energy values of lupin kernel meals when fed to rainbow trout. A series of 136 lupin kernel meals were assessed for their protein and energy digestibilities using the diet‐substitution approach in a series of 10 experiments over a 6‐year period from 2002 to 2008. Two reference diets were also included in each experiment. Minimal variance in the digestibility parameters of both reference diets was observed among the experiments ensuring that there was a high degree of robustness in the across‐experiment evaluations. The same lupin kernel meal samples were also scanned using a diode array near infrared spectrophotometer (DA‐NIRS). The spectra obtained by the DA‐NIRS were chemometrically calibrated against both the chemical composition and the digestible value data using multivariate analysis software. The cross validation tests used in this study provide a valid indication of the potential to predict the nutrient composition, energy value and digestible protein and energy values of the lupin kernel meals as used in diets for rainbow trout. That the standard errors of cross validation (SECV) of the parameters investigated were generally commensurate with the cross trial variation seen in the reference sample indicating robust calibrations for the two target parameters of digestible protein and digestible energy. Therefore this study demonstrates that within one raw material type that not only does significant variability in the digestible value of the raw materials exist, but that it is possible to use NIRS technology to provide rapid estimates of the digestible value of those raw materials in near real‐time.     

Effects of fish oil and partial fish meal substitution with oilseed oils and meals on growth performance, nutrient utilization and health of the rainbow trout Oncorhynchus mykiss

A feeding trial was conducted to investigate the effects of the replacement of dietary fish meal and fish oil with oilseed meals (soybean or canola) and canola oil on growth, nutrient utilization, body composition, diet digestibility and hematological parameters of rainbow trout Oncorhynchus mykiss. Seven diets were used; the control diet (designated FM) contained fish meal and fish oil as the main protein and lipid sources. For the experimental diets, 40% of fish meal protein was substituted with soybean meal, canola meal or a soybean/canola meal mixture, and these diets (designated SM, CM and SCM, respectively) contained fish oil as the lipid source. Three additional diets (SM?+?CO, CM?+?CO and SCM?+?CO) were formulated with the same vegetable protein meals but with fish oil replaced by canola oil. Fish were fed twice daily to apparent satiation for 11?weeks. The growth of fish fed the CM?+?CO diet was significantly lower than that of fish fed the FM, SCM, SM?+?CO and SCM?+?CO diets. The feed conversion ratio (FCR) was significantly better in fish fed the FM and SCM?+?CO diets than in fish fed the CM and CM?+?CO diets. Furthermore, feed intake was significantly lower for fish fed the CM?+?CO diet than in fish fed the SCM diet, and lipid digestibility of the CM?+?CO diet was significantly lower than that of all other diets. No significant differences of body composition were observed. Circulating leukocyte levels, leukocyte ratios and serum lysozyme activity remained unaffected by dietary treatment. However, it was observed that fish fed the CM?+?CO diet displayed hematocrit levels significantly lower (P?<?0.05) than that of fish fed the other diets. The results indicate that when diets contain either fish oil or canola oil, canola meal and soybean meal can be incorporated into rainbow trout feeds at a combined 32% inclusion level (replacing 40% of fish meal protein) without inducing significant negative effects on growth, nutrient utilization or health.     

Total fish meal replacement with canola protein isolate in diets fed to rainbow trout (Oncorhynchus mykiss W.)

The potential of canola protein isolate (CPI) as fish meal alternative in diets for rainbow trout was evaluated. Apparent digestibility coefficients (ADCs) for protein from a fish meal‐based reference diet (89.2 ± 1.1%) and CPI (84.6 ± 1.8%) were determined by indirect marker method in a digestibility experiment. ADC of dietary dry matter was slightly lower for the reference diet (62.5 ± 4.7%), but not significantly different to the CPI test diet (65.9 ± 3.1%). In a subsequent growth trial, 20 fish (initial weight 31.5 ± 0.5 g) were stocked into each of 15 experimental tanks of a freshwater flow‐through system. Fish were organized in triplicate groups and received experimental diets with 0%, 25%, 50%, 75% and 100% of fish meal replaced with CPI on the basis of digestible protein (designated as Control, I25, I50, I75, I100 respectively). At the end of a 70‐day feeding period, growth performance, feed intake and feed conversion ratio of treatment groups receiving diets I25, I50 or I100 were similar to the control group, while fish fed diet I75 showed significantly higher weight gain caused by improved feed conversion. The tested CPI was therefore identified to be a highly valuable fish meal alternative, not negatively affecting diet palatability, feed intake and feed efficiencies.     

Evaluation of full-fat and defatted maggot meals in the feeding of clariid catfish Clarias gariepinus fingerlings

The nutritional implication of processed maggot meals, hydrolysed, defatted, full‐fat, sun‐dried and oven‐dried, in the diets of Clarias gariepinus fingerlings were evaluated. The nutrient density, proximate composition, gross energy and mineral constituents of the maggot meals were determined. Five isonitrogenous and isocaloric diets were formulated to provide 40% crude protein in which fish meal in the reference diet was completely replaced by any of the following processed maggot meals: oven‐dried full‐fat (ODM), sun‐dried full‐fat (SDM), defatted oven‐dried (DODM) and defatted sun‐dried (DSDM) maggot meals respectively. Fish were fed ad libitum in triplicate treatments for 56 days in glass tanks. Biological evaluations of the fish were based on growth performance and nutrient utilization indices. The result of the nutrient composition analysis showed that processing methods of defattening and drying influenced the nutrient density of maggot meal, with crude protein content ranging between 43.30% and 46.70% for full‐fat sun‐dried and hydrolysed/defatted oven‐dried maggot meals respectively. The result showed that growth performance and nutrient utilization of fish fed DODM and DSDM dietary inclusions were not significantly different and similar to fish fed the fish meal‐based diet. However, fish fed the diet containing SDM exhibited lower daily weight gain, protein efficiency ratio and specific growth. Generally, fish performed better when fed diets containing defatted maggot meals than full‐fat maggot meal, and compared favourably with fish fed the fish meal‐based diet.     

Performance and sensory evaluation of silver perch (Bidyanus bidyanus Mitchell) fed soybean or meat meal-based diets in earthen ponds

The performance of silver perch fed a commercially available diet based on meat meal (38%), grain legumes (18%), oilseeds (10%), wheat millrun (20%), fishmeal (5%) and fish oil (3%) was compared with experimental diets based on alternative protein sources in two experiments. In Experiment 1, two experimental diets contained similar contents of fishmeal and fish oil as the commercially available reference diet, but soybean (25%) and wheat millrun (>31%) were used to reduce animal protein meals by approximately 50%. The digestible protein and digestible energy of the two experimental diets was either slightly lower (31.5% and 12.8 MJ kg^?1) or slightly higher (34.9% and 14.3 MJ kg^?1) than the reference diet (32.1% and 13.2 MJ kg^?1). In Experiment 2, the two experimental diets contained no fishmeal but included higher amounts of rendered animal meals (41–48%). One of the diets had similar digestible protein to the reference diet (32%) while the other had only 25% digestible protein. Silver perch (38 g for Experiment 1 and 59 g for Experiment 2) were stocked into each of nine 0.1 ha earthen ponds with fish in three ponds fed each diet for 191 days (Experiment 1) or 187 days (Experiment 2). Survival was >94% in all ponds in both experiments. In Experiment 1, growth rates and feed conversion ratios (FCRs) ranged from 2.1 to 2.4 g fish^?1 day^?1 and 1.7 to 1.9 respectively. Growth rates were significantly (P<0.05) lower for fish fed the experimental diet with the lowest digestible energy content. Growth rates for fish fed the other experimental diet and the reference diet were similar (P>0.05). In Experiment 2, growth rates and FCRs ranged from 2.3 to 2.4 g fish^?1 day^?1 and 1.6 to 1.7. There were no significant differences in fish performance indices for any of the three diets although experimental power was low (power=0.31). A blind consumer sensory evaluation (taste panel) of fish fed the three diets in Experiment 2 rated fish as ‘highly acceptable’. The diet with the lowest digestible protein content produced the best fish in terms of ‘smell liking’, ‘flavour liking’, ‘muddy flavour strength’ and ‘fresh flavour strength’. These results confirm that soybean meal and/or rendered animal protein ingredients including meat meal and poultry offal meal, and wheat can form the basis for high‐performance, low‐cost diets for intensive pond culture of silver perch.     

Evaluation of canola oils as alternative lipid resources in diets for juvenile red seabream, Pagrus auratus

This study examined three potential oil resources, crude and refined canola oil and refined soybean oil as replacements for added dietary fish oil in diets for juvenile red seabream. These oil resources were evaluated for their potential to replace added fish oil (40 g kg^?1) in fishmeal based (600 g kg^?1) diets, with 100 g kg^?1 of total lipids. Each of the three plant oils was used to replace 25%, 50%, 75% or 100% of the added dietary fish oil. Each of the three plant oils showed potential as a replacement for dietary fish oil, although a significant reduction in growth and feed utilisation was observed with the complete (100%) replacement of added fish oil by crude canola oil. No other significant effects of oil type or inclusion level on growth were apparent. A negative control (no added fish oil or plant oil, 60 g kg^?1 of total lipid) yielded poorer growth than all treatments except the diet containing 40 g kg^?1 of added crude canola oil (100% replacement). This observation confirmed that the added oils were utilized by the fish. A positive control diet containing 80 g kg^?1 of added fish oil (140 g kg^?1 total dietary lipid) sustained the best growth in the study, confirming that the 13 experimental diets were energy limiting as planned. Notably, few effects of the alternative oils were seen on the proximate composition of the fish. However, the influence of the alternative oils on the tissue fatty acid composition was considerable, irrespective of plant oil type or processing grade. Particularly notable was the overall increase in the level of polyunsaturated fatty acids in the tissues of the fish fed the plant oil diets, with these trends becoming more apparent with the greater levels of fish oil replacement. Minimal reductions in the levels of the long‐chain polyunsaturated fatty acids of eicosapentaenoic (20:5n‐3) and docosahexaenoic (22:6n‐3) acid were observed from any of the plant oil treatments. Sensory assessment, by an Australian taste panel, of the fish fed the fish oil reference, or the 100% replacement by refined canola or refined soybean diets showed a preference in order of canola oil > soybean oil > fish oil fed fish. Clearly, both canola and soybean oils have considerable potential as replacements of fish oils in diets for this species.     

Digestibility of Alternative Protein‐Rich Feedstuffs for Channel Catfish,Ictalurus punctatus

Apparent digestibility coefficients (ADCs) of amino acids, crude protein, gross energy, and dry matter of canola meal, corn gluten feed, fish offal meal, shrimp and fish offal meal, poultry by‐product meal, and hydrolyzed feather meal were determined for channel catfish, Ictalurus punctatus. Experimental diets contained 30% test ingredient, 69.5% casein‐based reference diet, and 0.5% chromic oxide. Groups of 20 fish (102.45 g) were fed the experimental diets twice a day at 3.5% body weight. Fecal samples were collected in triplicate daily at 0000 h and 0600 h after settlement into collection devices. Shrimp and fish offal meal and corn gluten feed presented significantly lower (P < 0.05) ADC for dry matter (59.5 and 39.3%) suggesting their low value as feedstuffs for catfish feeds. Although ADC values for crude protein were above 80% for all the test ingredients, amino acid digestibility varied significantly, except for histidine whose ADC remained constant regardless of the protein source. Lysine was the first limiting amino acid in most of the test ingredients, except in fish offal meal and poultry by‐product meal. Among the protein sources tested, only fish offal meal and poultry by‐product meal met channel catfish amino acid requirements for a 28% digestible protein grow‐out diet.     

Apparent digestibility of common feed ingredients by juvenile haddock, Melanogrammus aeglefinus L.

The digestible energy (DE) content and the apparent digestibility coefficients (ADCs) of nutrients in common feed ingredients available in Atlantic Canada for haddock, Melanogrammus aeglefinus, feed formulations were determined. Juvenile haddock (mean weight, 93.9±2.1 g) were held in tanks equipped with fecal collection columns and fed practical fish meal‐based diets for 5 weeks. The experimental diets consisted of a reference diet and six test diets, each containing 30% test ingredient, with all diets being supplemented with chromic oxide (Cr₂O₃, 5 g kg^?1) as the inert digestion indicator. Three marine fish by‐products, herring meal (HM), shrimp meal (SM) and crab meal (CRM) and three plant protein supplements, dehulled soybean meal (SBM), canola meal (CAM) and corn gluten meal (CGM) were the test ingredients. The DE content of HM, SBM, CGM, CRM, CAM and SM were 18.3, 18.0, 17.8, 12.4, 10.9 and 8.8 MJ kg^?1 respectively. Protein ADCs were 95.9%, 92.2%, 92.3%, 82.0%, 83.0% and 73.5% respectively. Organic matter ADCs were 95.9%, 89.0%, 72.6%, 68.9%, 58.9% and 54.9% respectively. Lipid ADCs were 97.9%, 83.0%, 57.4%, 62.0%, 87.2% and 55.8% respectively. Based upon its high crude protein content and nutrient ADC and DE content, properly processed dehulled SBM was found to be a good plant protein supplement to partially replace HM in haddock feeds.     

Evaluation of the feed value of a transgenic strain of the narrow‐leaf lupin (Lupinus angustifolius) in the diet of the marine fish,Pagrus auratus

This study assessed the nutritional and biological value of a noncommercial, transgenic line of the Australian sweet lupin, Lupinus angustifolius, (cv. Warrah), produced to increase the methionine content of the seed. An initial experiment demonstrated that differences in the methionine content of the transgenic and nontransgenic control lupins had no apparent influence on the growth of juvenile red seabream fed practical diets. Re‐evaluation of the nutritional characteristics of the lupin meals with subsequent digestibility studies allowed the determination of the digestible value of the protein and energy content of each of the varieties. The digestible protein content of either variety was similar, however significant differences in the digestible energy value of each variety existed (56.3% cf. 64.0%). This re‐evaluation of the nutritional value of the genetically manipulated (GM) and non‐GM lupin varieties enabled the reformulation of diets on a digestible protein and energy basis. A second growth trial was undertaken using sub‐satietal pair‐feeding regimes, with the experiment also involving protein‐restrictive diets to allow expression of the differences in the methionine content of the transgenic and nontransgenic lupin meals. A significant benefit of the enhanced methionine level in the transgenic lupin was observed. It is argued that in the high‐protein fish diets used, the importance of amino acid composition is relatively limited. Economic modelling of the potential value of the increased methionine in the transgenic lupin suggests that this will have limited benefit for aquaculture industries, and that greater value would be attributable to higher protein and energy levels in ingredients.     

Effects of cellulase addition to canola meal in tilapia (Oreochromis niloticus L.) diets

The effects of commercial cellulase enzyme products on the nutritive value of canola meal (CM) were determined in tilapia fry. Nine diets were prepared by adding cellulase enzyme (1–5 g kg^?1) to control diet (containing no canola), low canola (41.7 g kg^?1 CM) and high canola (208.3 g kg^?1 CM). Tilapia fry was fed for 90 days, and growth, feed conversion ratio (FCR), body composition and nutrient digestibility were determined. Fish fed the diets containing the lowest levels of canola meal (41.7 g kg^?1) had similar final weight and FCR relative to the group fed the control diet, and high canola diet showed significantly lower growth than other groups (P < 0.05), irrespective of cellulase enzyme. The addition of canola meal to tilapia diets resulted in lower protein digestibility and cellulose digestibility. There were no significant differences in body compositions in all treatments. Addition of enzymes to canola meal diets had no significant effects on growth performance, body compositions and nutrient digestibility. The results of this study indicate that use in higher level of canola meal in tilapia diet was adversely affected growth parameters and FCR. Adding dietary cellulase enzyme in different rations to diets showed no significant differences in growth parameter.