Digestibility of Dry Matter, Protein, Lipid, and Organic Matter of Two Fish Meals, Two Poultry By-product Meals, Soybean Meal, and Distiller's Dried Grains with Solubles in Practical Diets for Sunshine Bass, Morone chrysops ×M. saxatilis

Limited information is available on digestibility of nutrients in various practical ingredients used in diets for commercially important finfish species, such as hybrid striped bass. This information is especially needed for sunshine bass, Morone chrysops × M. saxatilis , to improve least-cost diet formulations and to allow effective substitution of feedstuffs. A study was conducted with large (867 g) sunshine bass to determine the apparent digestibility coefficients (ADCs) for moisture, protein, lipid, and organic matter (OM) in a variety of ingredients in floating, extrusion-processed, diets. The practical ingredients tested were menhaden (MEN) fish meal (FM), anchovy (ANCH) FM, pet-food grade poultry by-product meal, feed-grade poultry by-product meal, dehulled soybean meal (SBM), and distiller's dried grains with solubles (DDGS). Test diets consisted of a 70:30 mixture of reference diet to test ingredient with chromic oxide (1.0%) as the inert marker. Reference and test diet ingredients were mixed and extruded on a Wenger X85 single-screw extruder to produce floating pellets. The digestibility trials were conducted in twelve 1200-L circular tanks. Diets were randomly assigned to tanks of 30 sunshine bass and were fed once daily to satiation. Protein digestibility coefficients were significantly ( P  < 0.05) different among test ingredients and ranged from 86.42% for MEN to 64.94% for DDGS. Lipid ADCs were significantly different ( P  < 0.05) among test ingredients and ranged from 92.14% for MEN to 57.11% for SBM. OM ADCs were significantly different ( P  < 0.05) among test ingredients and ranged from 89.41% for MEN to 16.94% for DDGS. This information will assist in the formulation of more efficient, economical diets for sunshine bass.     

Apparent Digestible Energy Coefficients and Associative Effects in Practical Diets for Red Swamp Crayfish

Adult red swamp crayfish ( Procambarus clarkii ) were held in fecal collection chambers and fed common feedstuffs in two different types of diets, as the sole feedstuff and as a 30% substitution in a reference diet. Feedstuffs tested were soybean meal, peanut meal, wheat shorts, cooked corn, menhaden fish meal, and shrimp-head meal. Feed consumption, apparent digestible dry matter, and energy coefficients were determined for feedstuffs when fed in both diets. Addition of menhaden fish meal, shrimp-head meal, and peanut meal in the reference diet resulted in decreased consumption, and menhaden fish meal was poorly digested when incorporated at 30% in the reference diet. Apparent dry matter and energy digestion coefficients Indicated that plant feedstuffs have greater potential as ingredients in crayfish diets than feedstuffs of animal origin. Differences in consumption and digestibility between the two types of diet were observed. Therefore, it appears that the associative effects of additions of feedstuffs in diets should be considered when formulating crayfish feeds.     

Nutrient Digestibility of Cereal Grain Products and By‐products in Extruded Diets for Nile Tilapia

Apparent digestibility coefficients (ADCs) provide estimates of nutrient availability in feedstuffs and can be used as a tool for selecting ingredients to compound cost‐effective diets for fish. Extrusion process is one factor that could influence ADC values. Thus, a digestibility trial was undertaken to evaluate ADC of protein, energy, and dry matter, and apparent amino acid availability (AAAA) in five cereal grain products/by‐products (corn, wheat middlings, broken rice, rice bran, and sorghum) in compounded diets for Nile tilapia. Chromic oxide was used as an external inert marker. The digestibility values of energy and dry matter in ingredients, in decreasing order, were highest for broken rice (95.34 and 96.45%), sorghum (82.37 and 87.29%), corn (67.34 and 82.21%), rice bran (57.58 and 55.59%), and wheat middlings (48.94 and 45.88%). Protein digestibility value was higher for corn (72.86%) and the lowest value was observed for sorghum (56.77%), while broken rice, wheat middlings, and rice bran presented values ranging from 63.01 to 66.88%. AAAA values were higher for corn (70.05%) and the lowest methionine and cystine availability values were recorded for wheat middlings and broken rice, respectively. Broken rice appears as one of the most indicated ingredient for using in Nile tilapia diets because of its highest values of nutrient digestibility when compared to the other energetic sources. The use of this information should aid more precise and economic diet formulation for Nile tilapia.     

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.     

Apparent digestibility of selected ingredients in diets for white shrimp Penaeus setiferus L.

A study was conducted to determine apparent digestibility coefficients for dry matter (ADMD), crude protein (ACPD) and gross energy (AED) of selected ingredients in diets for juvenile Penaeus setiferus . Ingredients tested were corn grain, cottonseed meal, crab meal, grain sorghum, meat and bone meal, menhaden fish meal, rice bran, rice grain, shrimp meal, soybean meal, squid liver powder, wheat flour, wheat gluten, wheat middlings and wheat shorts. ADMD coefficients of test ingredients ranged from 22% to 100% and appeared to be related to the fibre, ash and starch content of the ingredient. ACPD coefficients ranged from 58% to 100%. Plant protein supplements (soybean meal and cottonseed meal) were utilized as efficiently as, or better than, animal protein supplements (squid liver powder, menhaden fish meal, meat and bone meal, shrimp meal and crab meal). ACPD coefficients for meat and bone meal, shrimp meal and crab meal (58–59%) were significantly lower than those for menhaden fish meal (76%) and squid liver powder (82%). AED coefficients (44–100%) varied significantly among plant products of similar proximate composition. Corn grain and wheat flour were better utilized by P. setiferus than other high-starch energy supplements. Wheat gluten exhibited the highest ADMD, ACPD and AED coefficients of all ingredients tested.     

Evaluation of Methods for Determining In Vivo Digestion Coefficients for Adult Red Swamp Crayfish Procambarus clarkii

Adult red swamp crayfish ( Procambarus clarkii ) were held in fecal collection chambers and fed common feedstuffs isosubstituted in experimental diets. Apparent dry matter digestibility (ADMD) and apparent crude protein digestibility (ACPD) coefficients were determined by the total collection and indicator (chromic oxide) methods. Feedstuffs tested were menhaden fish meal, soybean meal, alpha-soy protein, casein, gelatin, wheat bran, rice bran, wheat gluten, shrimp meal, crab chitin, cellulose, squid meal, corn starch and diatomaceous sand. Rate of consumption of plant feedstuffs was generally higher than feedstuffs of animal origin. Consumption of fish meal and shrimp meal was low (0.59 and 0.44% body weightlday, respectively). Fecal chromium concentrations were lower than chromium concentrations of experimental diets and precluded calculation of realistic coefficients by the indicator method. Analysis of refused feed samples indicated that crayfish did not consume the indicator in the same proportion as the remainder of the diet; therefore, the total collection method was judged the better approach to determining digestion coefficients. ADMD and ACPD coefficients of plant feedstuffs were generally higher than coefficients determined for animal feedstuffs. ADMD coefficients indicated substantial carbohydrate digestion by crayfish.     

Minimizing Fish Oil and Fish Meal with Plant‐based Alternatives in Sunshine Bass Diets without Negatively Impacting Growth and Muscle Fatty Acid Profile

We determined whether canola oil could spare menhaden oil (MO) in diets containing minimal fish meal without affecting sunshine bass, Morone chrysops × Morone saxatilis, production. Seven isonitrogenous, isocaloric (41.7% crude protein and 14.6% crude lipid) diets containing graded levels (0, 20, 40, 60, 80, or 100%) of menhaden to canola oils with 20% menhaden meal (MM) or 100% canola oil with 20% lipid‐extracted MM were fed to sunshine bass (initial weight 9.3 ± 0.16 g; mean ± SD) twice daily to apparent satiation for 10 wk. Sunshine bass fed less than 40% of their dietary lipid as MO exhibited significantly (P < 0.05) lower feed intake and growth rates. Increased concentrations of saturated, n‐3, and n‐3 highly unsaturated fatty acids (FA) in the fillet were associated with MO‐rich diets, while monounsaturated and n‐6 FA were most common in fillets from fish fed diets rich in canola oil. Reducing MO to 40% of the dietary lipid in diets containing minimal fish meal allows for efficient utilization of marine resources without negatively impacting juvenile sunshine bass production.     

Apparent digestibility coefficients of feed ingredients and their prediction in diets for tilapia Oreochromis niloticus×Oreochromis aureus (Teleostei, Cichlidae)

Apparent digestibility of crude protein (CP), lipid, carbohydrate, energy and fatty acids was measured in various feed ingredients fed to hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) including fish and poultry meals, corn gluten, soybean meal, rapeseed meal, sunflower seed meal, wheat, corn, sorghum, barley and wheat bran. Chromic oxide was used as a non‐absorbed marker. A diet compounded from a mixture of these ingredients was then used to examine the possibility of predicting the digestibility of formulated diets. In addition, the effect of pelleting or extrusion on digestibility of a compound diet was examined. Apparent digestibility of CP ranged from 75% to 97%, lipids from 72% to 90% and energy from 39% to 89% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 32% to 80%. Digestibility of fatty acids ranged from 75% to 90% with saturated fatty acids exhibiting digestibilities lower than unsaturated fatty acids. In a full‐fat soy diet containing 19% fat, digestibility of lipids did not decrease. There were no significant differences in digestibility between a diet that was either pelleted or extruded. Tests conducted using a compound diet indicated that ingredient digestibility was additive for protein, lipids carbohydrates and energy. Diets for the hybrid tilapia may thus be formulated on the basis of digestibility of individual ingredients, for the nutrients examined in this study.     

Amino acid availability from animal, blended, and plant feedstuffs for hybrid striped bass (Morone chrysops × M. saxatilis)

The refinement of hybrid striped bass feed formulations has been progressing rapidly. There is still, however, limited information available regarding nutrient digestibility and amino acid availability from common feedstuffs. A pair of experiments was conducted to determine the protein digestibility and amino acid availability to sunshine bass from an assortment of commercially available animal protein feedstuffs, blended animal products and plant protein feedstuffs in extruded diets. The feedstuffs tested were blood meal, poultry by‐product meal, fish solubles, Pro‐Pak 60, Pro‐Pak 65, ProCon 65RDB, and 60FMC for the animal protein feedstuffs and brewer's yeast, canola meal, peanut meal, and sunflower meal for the plant protein feedstuffs. Test diets consisted of a mixture of nutritionally complete reference diet and test ingredient. Triplicate tanks of fish were fed their respective diets for 7 days prior to collection of faeces by stripping. Apparent digestibility coefficients of protein (ADC‐CP) in the animal products ranged from 47% for 60FMC to a high of 70% for fish solubles. ADC‐CPs for animal products were not different across products. Blood meal, poultry by‐product meal, Pro‐Pak 60, Pro‐Pak 65, and ProCon had intermediate ADC‐CPs of 63, 55, 63, 57 and 52%, respectively. ADC‐CP in plant feedstuffs ranged from 43% for canola meal to 80% for peanut meal. Brewer's yeast, canola meal, and sunflower meal had intermediate ADC‐CPs at 54, 43 and 69%, respectively. Apparent amino acid availability coefficients were variable across animal products and did not necessarily correlate to the ADC‐CPs for a given feedstuff. Isoleucine availability was low in blood meal at 38% compared with 59% or better for the remaining amino acids. Lysine, tyrosine and phenylalanine availability from fish solubles was low at 31, 35 and 44%, respectively. Amino acid availability from Pro‐Pak 60 was consistently higher across all amino acids for the animal products and blends tested. Of the plant products tested, peanut meal was the best performing feedstuff relative to amino acid availability.     

Apparent digestibility of alternative plant‐protein feedstuffs for channel catfish,Ictalurus punctatus (Rafinesque)

A study was conducted with channel catfish, Ictalurus puntatus to determine apparent digestibility/availability coefficients of protein, amino acids, lipid and energy for alternative plant‐protein feedstuffs: corn gluten feed, corn germ meal, distillers dried grains with solubles, and canola meal, compared with those for soybean meal. A 32%‐protein, chemically defined diet containing 8% fish meal was used as the reference diet. Test diets consisted of 70:30 ratio of reference diet to test ingredient with chromic oxide (0.75% of the diet) as an inert indicator. Apparent digestibility/availability coefficients of protein, essential amino acids and energy in alternative protein feedstuffs tested were generally lower than those in soybean meal by channel catfish. Apparent digestibility coefficients of protein ranged from 75 to 87% and those of energy ranged from 52 to 59% for alternative feedstuffs. Lysine in alternative feedstuffs was 67–79%, methionine was 69–85% and cystine was 73–82% available to channel catfish. There were no significant differences in lipid ADCs among test feedstuffs (91.9–96.8%). Results from the present study can be useful in formulating cost‐effective catfish feeds using these alternative feedstuffs.     

Effects of varying dietary compositions using common feed ingredients on growth and feed efficiency of pond‐raised channel catfish Ictalurus punctatus (Rafinesque)

Two experiments were conducted to evaluate various ingredient combinations in a 28% or 32% protein diet for optimum performance of channel catfish Ictalurus punctatus. All diets contained soybean meal and corn, but with or without cottonseed meal, wheat middlings or fish meal (FM). Channel catfish fingerlings were stocked into 0.04 ha earthen ponds at 18 530 fish ha^?1. Fish were fed one of eight diets once daily to apparent satiation for two growing seasons. Results demonstrated that the dietary ingredient composition used had significant effects on fish performance, but magnitude of differences was relatively small. Overall, diets containing FM resulted in greater weight gain (Experiments 1 and 2) and lower feed conversion ratio (Experiment 1) than fish fed all‐plant diets. However, certain combinations of plant ingredients provided the similar fish growth as some diets containing FM. There were no significant differences in weight gain between fish fed soybean meal–corn or soybean meal–corn–wheat middlings‐based diets with cottonseed meal or FM. The use of wheat middlings in the diet had no significant effects on fish production characteristics.     

Carbohydrate and lipid digestibility of animal and vegetal ingredients and diets for juvenile Australian redclaw crayfish, Cherax quadricarinatus

Carbohydrate and lipid digestibility of three vegetal and four animal ingredients, and diets in which they were included, were evaluated for juvenile Australian redclaw crayfish, Cherax quadricarinatus. The ingredients were: soy paste, textured wheat, sorghum meal, sardine meals (67% and 58% crude protein), squid meal and red crab meal. A basal diet was formulated, and then seven experimental diets were created, including 150 g kg^?1 of each ingredient in the reference diet. Digestibility was measured in vivo, using chromic oxide as marker. A single‐factor, completely randomized experimental design with three replicates per treatment was performed. Mean carbohydrate digestibility of vegetal ingredients and the corresponding diets was better than carbohydrate digestibility of animal ingredients. Sorghum meal had a carbohydrate digestibility over 94%, and the diet in which it was included over 92%. Soy paste and wheat meals also presented excellent carbohydrate digestibility (around 88% for ingredients and over 90% for diets). Mean carbohydrate digestibility of animal ingredients and their corresponding diets were very poor (from 18% to 32%) and this affected the carbohydrate digestibility of diets in which they were included (87–89%). Lipid digestibility was also better for vegetal ingredients. Soy paste and wheat meal recorded values over 93% and their diets over 94%. Sorghum lipid presented slightly lower digestibility. Some of the animal ingredients, especially red crab, had an excellent lipid digestibility (92.1%).     

A comparison of two faecal collection methods for protein and amino acid digestibility coefficients of menhaden fish meal and two grades of poultry by-product meals for market-size sunshine bass (Morone chrysops × M. saxatilis)

Apparent digestibility and availability coefficients for protein and amino acids in menhaden fish meal (MEN), pet‐food grade (PBM‐pet,) and feed‐grade poultry by‐product meal (PBM‐feed) were determined for market‐size (500 g) sunshine bass in two consecutive trials using passive netting (1.6 mm mesh) followed by manual stripping of faeces. A reference diet resembling a commercial feed was formulated to meet or exceed all known nutritional requirements of hybrid striped bass. Test diets were formulated to contain a 70 : 30 mixture of reference diet to test ingredient with chromic oxide (1%) serving as the inert marker. Diets were extruded under commercial conditions and the reference diet was fed for two weeks in order to acclimate fish to experimental conditions. Each diet was randomly assigned to triplicate tanks containing 30 fish each. Fish were fed their respective diet twice daily to apparent satiation for two weeks, with faecal collections being conducted on the 7th and 14th day, in each trial. ADC values determined in the net method were highly variable and generally lower than ADCs obtained by stripping. Consistently lower and highly variable chromium concentrations were found in the net method faecal samples and suggest that marker loss relative to nutrient content, or dilution of marker with non‐faecal matter, on the net collectors influenced results in that trial. In contrast, the standard errors of ADCs determined in the strip method were less than 5 percentage points in most cases. Protein digestibility ranged from a low of 51% (PBM‐feed) to a high of 87% (PBM‐pet) in the net method, and from a low of 80% (PBM‐feed) to a high of 99% (MEN) in the strip method. With the exception of Lys, no differences in amino acid availabilities among diets were found in the net method. In the strip method, protein digestibility and amino acid availabilities in MEN were generally greater than those found in PBM‐pet or PBM‐feed, whereas ADCs were not significantly different between the two poultry by‐products. Based on the conditions of the present study, net collection of faecal matter can not be recommended for determining the digestibility of nutrients in feed ingredients for market‐size sunshine bass. Digestibility coefficients obtained by the strip method for feed and petfood grades poultry by‐product were higher than those previously reported and will be facilitate more efficient and economical diet formulations for larger sunshine bass.     

Carbohydrate and lipid digestibility of animal and vegetal ingredients and diets for the pre-adult redclaw crayfish, Cherax quadricarinatus (von Martens)

In vivo carbohydrate and lipid digestibility of four animal [sardine meals 67% and 58% crude protein (CP), squid meal and red crab meal] and three vegetal (soy paste, textured wheat and sorghum meal) ingredients and diets were evaluated in experimental diets for pre-adult redclaw crayfish, Cherax quadricarinatus . A reference and seven experimental diets were formulated, including 14.5% of each ingredient in the reference diet. A single factor, completely randomized experimental design with five replicates per treatment was done. Experimental organisms were pre-adult redclaw of 10±0.8 g. The best carbohydrate digestibilities were recorded for some vegetal ingredients such as sorghum and textured wheat (93.6% and 83.9%) and the corresponding diets (90.9% and 90.8%). For animal ingredients, carbohydrate digestibilities were very poor (from 12.3% to 41.1%), and the inclusion of these ingredients diminished the digestibility of the corresponding experimental diets as compared with the reference diet (86.3–89.2% vs. 89.9%). The highest lipid digestibility corresponded to red crab meal (97.5%). Textured wheat and soy paste meal also had excellent lipid digestibility (96.4% and 95.1%). The same tendency was found for the corresponding diets. The lowest percentages were obtained with 58% crude protein sardine meal (32.9%) and its diet (86.2%).     

Apparent digestibility of selected feed ingredients for white shrimp Litopenaeus vannamei,Boone

Apparent digestibility coefficients of dry matter (DM), crude protein, crude lipid, gross energy, phosphorus and amino acids in Peruvian fish meal (FM), fermented soybean meal, extruded soybean meal, soybean meal, peanut meal, wheat gluten meal, corn gluten meal, shrimp byproduct meal, meat and bone meal (MBM), poultry meat meal and plasma protein meal (PPM) were determined for white shrimp (Litopenaeus vannamei). A reference diet (RF) and test diets (consisting of 70% RF diet and 30% of the feedstuff) were used with 0.5% chromic oxide as an external indicator. A total of 1440 shrimp (initial mean body weight 1.05 ± 0.01 g) were randomly stocked into thirty‐six 500‐L fibreglass tanks with 40 shrimp per tank and three tanks per diet. Faeces were collected from triplicate groups of shrimp by a faecal collection vessel attached to the shrimp‐rearing tank. The shrimp were fed to apparent satiation four times a day and the feeding experiment lasted for 6 weeks. Statistics indicate that apparent DM digestibilities for white shrimp (L. vannamei) were the highest for FM, ranged 52.83–71.23% for other animal products and 69.98–77.10% for plant products. The protein and lipid from plant and animal sources were well digested by white shrimp. Apparent protein and lipid digestibility were in the range 87.89–93.18% and 91.57–95.28%, respectively, in plant products, and 75.00–92.34% and 83.72–92.79%, respectively, for animal products. The white shrimp demonstrated a high capacity to utilize phosphorus in the ingredients. The apparent phosphorus digestibility ranges of animal feedstuffs and plant feedstuffs were 58.90–71.61% and 75.77–82.30% respectively. Amino acid availability reflected protein digestibility, except that in MBM, for which the availability of some amino acid was lower, possibly due to protein damage during processing. Digestibility information could promote the use of ingredient substitution in least‐cost formulated diets for white shrimp.     

The effect of phytase on apparent digestibility of four practical plant feedstuffs fed to striped bass, Morone saxatilis

This study was conducted to determine the effect of phytase on apparent dry matter (DM), crude protein and phosphorus (P) digestibility of four plant feedstuffs (isolated soya protein, ISP; soyabean meal, SBM; corn gluten meal, CGM and wheat middlings, WM) fed to striped bass Morone saxatilis . One reference diet was formulated based solely on animal feed ingredients. Four test diets were prepared by mixing 60–75% of the reference diet with 40–25% of the test ingredient in order to reach similar levels of total P (0.67–0.73%) and to have a minimum of 35% protein (36.1–53.0%). Chromic oxide was added at 0.5% of the diet and used as an indigestible marker. A phytase solution was sprayed postpelleting on the test diets at a concentration of 1000 phytase units kg⁻¹ (PU kg⁻¹) dry diet. The test diets (with or without phytase supplementation) and the reference diet (nine treatments total) were fed to 3-year-old striped bass and were replicated in time ( n =3) during the 4-week period. Digestibility of DM was significantly lower ( P  < 0.001) for SBM and WM when compared with CGM and ISP and was not influenced by phytase supplementation. Crude protein digestibility was also not affected by phytase supplementation and was significantly lower ( P  < 0.09) for SBM when compared with ISP. Phosphorus digestibility was improved by approximately 23% with the addition of phytase for all four feedstuffs tested ( P  < 0.001). Furthermore, WM had significantly lower ( P  < 0.0001) P digestibility when compared with the other feedstuffs, irrespective of phytase supplementation.     

Apparent digestibilities of common feedstuffs for bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides using individual test ingredients

Apparent digestibility of dry matter and energy, and availability of amino acids from blood meal (BM), fish meal (FM), meat and bone meal (MBM), poultry by-product meal (PBM), soybean meal (SBM), corn, wheat and yellow grease (YG) were determined for bluegill Lepomis macrochirus (mean weight, 57 g), and likewise, but not for BM or wheat, for largemouth bass Micropterus salmoides (mean weight, 30 g). To avoid nutrient interaction from a reference diet, diets containing 98.5% (985 g kg⁻¹) of test ingredients were used, except for semi-solid, YG which was mixed with corn to permit pelletization. Faeces were collected by a siphoning method. Apparent dry matter digestibility values ranged from 50% (corn) to 87% (BM) for bluegill and from 53% (MBM) to 76% (PBM) for largemouth bass. Apparent energy digestibility values ranged from 53% (corn) to 92% (BM) for bluegill and from 63% (MBM) to 93% (YG) for largemouth bass. Apparent digestibility of most amino acids exceeded 90% for evaluated protein sources, except for MBM which showed slightly lower values (80–90%) for both fishes. Isoleucine digestibility from BM was relatively low (82%) for bluegill. High digestibility values for SBM, PBM and BM, indicate good potential for replacing FM in diets for both fishes.     

Amino acid availability from selected animal‐ and plant‐ derived feedstuffs for market‐size sunshine bass (Morone chrysops × Morone saxatilis)

A study was conducted with market‐size (867 g) hybrid striped bass to determine the nutrient digestibility and apparent amino acid availability of six common feedstuffs. The animal‐protein feedstuffs tested were menhaden fish meal (MEN), anchovy fish meal (ANCH), pet‐food grade poultry by‐product meal (PBM‐pet), and feed‐grade poultry by‐product meal (PBM‐feed), while the plant‐protein feedstuffs were dehulled solvent extracted soybean meal (SBM) and distiller’s dried grains with solubles (DDGS). Test diets consisted of a 70 : 30 mixture of reference diet to test ingredient with chromic oxide (10 g kg^?1%) as the inert marker. Diets were randomly assigned to triplicate tanks of fish that were fed their respective diets for 7 days prior to fecal collection by stripping. Two feeding trials were conducted sequentially to determine the digestibility of the six test ingredients. In trial 1, the three ingredients evaluated were MEN, PBM‐feed, and PBM‐pet. In trial 2, the three ingredients evaluated were ANCH, SBM, and DDGS. Apparent digestibility coefficients of protein (ADC‐CP) were significantly (P < 0.05) different among test ingredients in trial 1 as protein digestibility of MEN (86%) was significantly higher (P < 0.05) than that of PBM‐feed (75%), but was not significantly different from that of PBM‐pet (78%). Protein digestibilities in trial 2 were not significantly different among test ingredients and averaged 76% for ANCH, SBM, and DDGS. Some apparent amino acid availability coefficients differed among feedstuffs for both trial 1 and trial 2. MEN provided higher amino acid availabilities for alanine, aspartic acid, glutamic acid, lysine, valine, and tryptophan (99%, 98%, 94%, 96%, 99%, and 108%, respectively) when compared to PBM‐feed (73%, 50%, 69%, 80%, 77%, and 91%, respectively) and PBM‐pet (79%, 66%, 81%, 81%, 78%, and 99% respectively). Glycine, histidine, leucine, and proline availabilities in MEN (95%, 96%, 100%, and 98%, respectively) were significantly (P < 0.05) higher than those of PBM‐feed (64%, 82%, 82%, and 57%, respectively), but were not significantly different from PBM‐pet (85%, 92%, 89%, and 80%, respectively). For trial 2, apparent amino acid availabilities for cystine, isoleucine, lysine, and tyrosine were significantly higher (P < 0.05) among treatments fed SBM (100%, 87%, 93%, and 97%, respectively) and ANCH (37%, 95%, 92%, and 84%, respectively) compared to treatments fed DDGS (?13%, 52%, 62% and 62%, respectively). Overall, amino acid availability in SBM and the two PBM’s appear comparable to MEN and ANCH and corroborate their high value as potential replacements for fish meal in sunshine bass diets. However, DDGS provided the lowest availabilities for several amino acids and should be used with caution.     

Apparent digestibility coefficients of selected protein feed ingredients for loach Misgurnus anguillicaudatus

Apparent digestibility coefficients of dry matter, crude protein, lipid and energy, and amino acids availability in white fish meal, brown fish meal, meat meal, fermented soybean meal, soybean meal and rapeseed meal were determined for loach (Misgurnus anguillicaudatus) (12.05 ± 0.21 g), using a reference diet with 5 g kg^?1 chromic oxide and test diets that contained 700 g kg^?1 reference diet, by weight, and 300 g kg^?1 of the test feed ingredients. The juvenile loach was held in 300‐l tanks at a density of 30 fish per tank. White fish meal, brown fish meal, meat meal and fermented soybean meal had highest apparent digestibility coefficients (ADCs) of dry matter, crude protein and gross energy among ingredients tested, ranged from 50.4% to 60.9% for dry matter, from 64.6% to 88.4% for crude protein and from 57.9% to 79.0% for gross energy. The apparent digestibility coefficients of dry matter ranged from 61.0% to 66.9% for animal products and 50.4% to 60.7% for plant products. For crude protein, apparent digestibility coefficients of protein exceeding 80% were observed for white fish meal, brown fish meal, meat meal and fermented soybean meal, and the apparent digestibility coefficients of protein in rapeseed meal were the lowest among all the treatments. Lipids from both animal and plant feedstuffs were poorly digested by loach, ranging from 64.0% to 77.6%. The apparent digestibility coefficients of energy were similar to those of dry matter and protein, and the highest and lowest ADCs of energy were found in WFM and RM, respectively. The loach used dietary phosphorus from the animal feedstuffs more efficiently than from plant feedstuffs (soybean meal and rapeseed meal), with ADC‐values ranging from 42.3% to 53.1% and from 25.1% to 32.7%, respectively. For the animal products, the availabilities of amino acids in white fish meal and brown fish meal were higher than that in meat meal, expect for Met, Asp, Pro, Gly, and Cys. Among all the plant products, the availabilities of amino acids in fermented soybean meal were higher than in soybean meal and rapeseed meal, and thus had a greater potential to be used as a dietary replacement of fish meal in loach diets.     

Use of Corn Germ Meal in Diets for Pond‐Raised Channel Catfish,Ictalurus punctatus

Corn germ meal (CGM) is a by‐product of corn milling. On the basis of its nutrient composition and digestibility values, it appears to be a suitable ingredient for use in channel catfish, Ictalurus punctatus, diets. A study was conducted to examine the use of various levels of CGM in diets for pond‐raised channel catfish. Four 28% protein diets containing 0, 15, 25, and 35% CGM were evaluated. Fingerling channel catfish (mean initial weight: 71 g/fish) were stocked into 24, 0.04‐ha ponds at a rate of 14,826 fish/ha. Fish were fed once daily to apparent satiation for a 167‐d growing season. No significant differences were observed in total amount of diet fed, diet consumption per fish, net yield, weight gain, feed conversion ratio, survival, fillet yield, and fillet protein, fat, and moisture concentrations among fish fed diets containing various levels of CGM. Carcass yield decreased linearly as dietary CGM levels increased. Depending on prices, CGM can be used interchangeably with corn gluten feed in channel catfish diets as replacements for corn, wheat middlings, and soybean meal to reduce feed cost.