Effect of dietary fish meal replacement by red algae, Gracilaria arcuata, on growth performance and body composition of Nile tilapia Oreochromis niloticus

A 12-week long feeding experiment was initiated to evaluate the effect of dietary supplementation of red algae, Gracilaria arcuata, on the growth performance, feed utilization and body composition of Nile tilapia Oreochromis niloticus (Linnaeus, 1758). The fish were fed with an algae-free control diet (C) and three experimental diets which replaced conventional fish meal with varying levels of dried G. arcuata (20%, 40% and 60%, represented as G20, G40 and G60, respectively). The growth parameters of final weight (FW), weight gain (WG), percentage of weight gain (WG%), daily growth rate (DGR) and specific growth rate (SGR) were significantly reduced (P < 0.05) at all levels of algae incorporation compared to the control diet. Moreover, the negative impact of Gracilaria meal on the growth performance of Nile tilapia increased as the proportion of algae in the diet increased, with fish on diet G20 exhibiting a significantly higher growth performance than the fish on either of the G40 and G60 diets. On the other hand, the feed utilization parameters feed conversion ratio (FCR) and protein efficiency ratio (PER) did not show significant differences between the fish in the control group and those on diet G20, although poorer FCR and PER outcomes were achieved in the case of fish on diet G60. The content of moisture, protein and ash in muscle and carcass increased as the proportion of Gracilaria meal in the diets increased, but the reverse was true for lipid level. These results indicate that incorporation of less than 20% red algae, Gracilaria arcuata, could be feasible in the diet of Nile tilapia and further studies are recommended to optimize the level of algae to improve growth performance.     

Effect of water temperature,feeding frequency,and protein percent in the diet on water quality,growth and behavior of Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

This study evaluated how water temperature (26, 28, and 30°C), number of meals per day (one or two meals), and protein percent in diet (20, 25 and 30%) impact growth performance, biometric indices, and feeding behavior of Nile tilapia, Oreochromis niloticus. Fish were randomly allocated into 18 equal replicate groups. Higher final body weight was observed in fish reared at 30°C and fed one meal per day containing 30% crude protein. Better weight gain, weight gain %, feed conversion ratio, specific growth rate, and condition factor were recorded in fish reared at 26°C and fed one meal per day containing 30% protein. The best length weight relationship was obtained in fish reared at 26°C and fed one meal per day containing 30% crude protein. Shorter feeding duration and duration of appetite inhibition latency were recorded in fish reared at 30°C, fed one meal per day, and given a diet containing 30% protein. The highest proactivity was recorded in fish reared at 30°C, received one meal per day, and with 25% crude protein in their diet. Conclusively, rearing Nile tilapia at 26–30°C with a lower feeding frequency (one meal/day) and a 30% crude protein diet achieved better performance and feeding behavior.     

Pterocladia (Rhodophyta) and Ulva (Chlorophyta) as feed supplements for European seabass, Dicentrarchus labrax L., fry

The aim of this study was to evaluate the suitability of two marine macroalgae, Ulva lactuca (Chlorophyta) and Pterocladia capillacea (Rhodophyta), meals as a supplement to enhance the nutritional value of formulated feeds for European seabass Dicentrarchus labrax fry. Seven isoproteic (50 % crude protein), isocaloric (500 Kcal/100 g gross energy) diets containing four levels (0 or control, 5, 10, and 15 %) of either Ulva meal (UM) or Pterocladia meal (PM) were tested. Each diet was fed to triplicate groups of D. labrax fry (initial body weight, 0.23?±?0.02 g for Ulva- and 0.14?±?0.01 g for Pterocladia-fed fish), to apparent visual satiety for 8 weeks. The results indicated that feeding seabass at 5 % UM or PM level (U₅ and P₅ diets) produced the best growth, feed utilization, nutrient retention, and survival rates among all the dietary groups. Feeding fish with a 5 % PM-added diet has also improved stress response after a 5-min air exposure test, prior to the termination of the feeding trial. These findings suggest that both Pterocladia and Ulva meals could be potentially used as an additional feed component (at 5 %) for enhancement of seabass D. labrax fry performance, nutrients composition, and stress resistance especially when subjected to transportation from hatchery to weaning ponds/tanks.     

Effect of feeding pineapple waste on growth performance,texture quality and flesh colour of nile tilapia (Oreochromis niloticus) fingerlings

The study aims to evaluate the effects of pineapples waste on the growth, texture quality and flesh colour of Nile tilapia (Oreochromis niloticus) fingerlings. Fingerlings were fed with four different levels of pineapple waste diets throughout 56 days, which contain a control group (Diet 1) and experimental diets that formulated with 10% (Diet 2), 20% (Diet 3) and 30% (Diet 4) of pineapple waste. The experimental diet was formulated with rice bran, fish meal, soybean meal, vitamin and mineral premix, vegetable oil and binder to attain 32% dietary protein. The results revealed that the formulated fish diet with pineapple waste given the optimum weight gain, weight gain percentage, specific growth rate than the control group, where Diet 4 has shown the highest value (p < 0.05). There were no effects of the pineapple waste diet on the texture quality of the fillet, while only red chromaticity (a*) showed a significant difference (p < 0.05). In conclusion, the addition of pineapple waste can improve the growth rate of Nile tilapia, and the supplementation level of the pineapple waste in the diet was 30% of the total feed formulation.     

Pea protein concentrate in diets for sharpsnout sea bream (Diplodus puntazzo): effects on growth and health status

Four diets for sharpsnout sea bream juveniles (14 g body weight) with four levels of air-processed pea protein concentrate (PPC) (0, 160, 320 and 487 g/kg diet) were tested in triplicate. The experimental diets were isonitrogenous (43% crude protein) and isolipidic (19% ether extract) and the fish were fed to satiation twice a day. After 125 d, fish growth was diminished by the inclusion of PPC. Feed conversion did not show significant differences in any treatment. Neither the body analyses nor the protein and individual essential amino acid retention efficiencies were affected by the inclusion of PPC in the diet. However, histological gut examinations revealed noticeable differences. Fish fed the diet with the highest inclusion level of PPC presented the longest villous length and the most goblet cells, and the width of the lamina propria increased in the anterior intestine. Although no negative changes in nutritive parameters were detected, these alterations might affect nutrient transport, with negative consequences for fish growth. It was concluded that the PPC in the amounts tested here is an inappropriate substitute for fishmeal in diets for sharpsnout sea bream juveniles.     

Effect of replacing different levels of dietary fishmeal with Jatropha curcas kernel meal on the development of Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

The present trial tested the applicability of Jatropha curcas kernel meal (JKM) as a protein source in diets for Nile tilapia (Oreochromis niloticus) in terms of growth and body composition. Four diets were produced replacing 0% (Control), 50% (J50), 75% (J75) and 100% (J100) of fishmeal with JKM. In a fifth diet, 70% of fishmeal was replaced by JKM, and another 20% replaced by blood meal to minimize crystalline lysine addition. Body mass gain of fish fed the control diet was significantly higher than in all other treatments. However, specific growth rate (SGR) and feed conversion ratio (FCR) were not significantly different between diets J50, J75 and the control. Fish fed the control diet had a lower body protein content, but higher body fat and energy content than fish fed the JKM‐based diets. An adaptation of fish fed diets J50, J75 and J100 could also be observed, as these diets showed worse FCR‐values over most of the first three quarters of the experiment and equal (or in the case of J75, even significantly better) FCR‐values over the final 2 weeks. Despite slightly slower growth, JKM should be further included in the search of alternative plant‐feedstuffs in diets for tilapia, as the growth observed here for up to 75% replacement of fishmeal was very promising.     

Dietary protein modulates digestive enzyme activities and gene expression in red tilapia juveniles

It is known that the level of dietary protein modulates the enzymatic activity of the digestive tract of fish; however, its effect at the molecular level on these enzymes and the hormones regulating appetite has not been well characterised. The objective of this study was to evaluate the effect of CP on the activity of proteases and the expression of genes related to the ingestion and protein digestion of juveniles of red tilapia (Oreochromis sp.), as well as the effects on performance, protein retention and body composition of tilapia. A total of 240 juveniles (29.32 ± 5.19 g) were used, distributed across 20 tanks of 100 l in a closed recirculation system. The fish were fed to apparent satiety for 42 days using four isoenergetic diets with different CP levels (24%, 30%, 36% and 42%). The results indicate that fish fed the 30% CP diet exhibited a higher growth performance compared to those on the 42% CP diet (P < 0.05). Feed intake in fish fed 24% and 30% CP diets was significantly higher than that in fish fed 36% and 42% CP diets (P < 0.05). A significant elevation of protein retention was observed in fish fed with 24% and 30% CP diets. Fish fed with 24% CP exhibited a significant increase in lipid deposition in the whole body. The diet with 42% CP was associated with the highest expression of pepsinogen and the lowest activity of acid protease (P < 0.05). The expression of hepatopancreatic trypsinogen increased as CP levels in the diet increased (P < 0.05) up to 36%, whereas trypsin activity showed a significant reduction with 42% CP (P < 0.05). The diet with 42% CP was associated with the lowest intestinal chymotrypsinogen expression and the lowest chymotrypsin activity (P < 0.05). α-amylase expression decreased with increasing (P < 0.05) CP levels up to 36%. No significant differences were observed in the expression of procarboxypeptidase, lipase or leptin among all the groups (P > 0.05). In addition, the diet with 42% CP resulted in a decrease (P < 0.05) in the expression of ghrelin and insulin and an increase (P < 0.05) in the expression of cholecystokinin and peptide yy. It is concluded that variation in dietary protein promoted changes in the metabolism of the red tilapia, which was reflected in proteolytic activity and expression of digestion and appetite-regulating genes.     

The red alga Porphyra dioica as a fish-feed ingredient for rainbow trout (Oncorhynchus mykiss): effects on growth, feed efficiency, and carcass composition

Porphyra dioica meal was added at levels of 5, 10 and 15% to a diet for rainbow trout formulated to be isonitrogenous and isolipidic. The control diet was a commercial trout diet without seaweed meal. The experimental groups were fed in triplicate for 12.5 weeks, during which fish weight increased on average from 107–261 g. Seaweed meal inclusion did not affect significantly weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER) and apparent digestibility coefficient of the dry matter (ADC_dm) for any of the diets. Voluntary feed intake (VFI) increased for all seaweed diets compared to the control diet but not significantly (P?>?0.05). Final weight (FW) was significantly smaller for the 15% P. dioica inclusion and hepatosomatic index (HSI) for the 10% and 15% inclusion. Carcass protein content increased for all three experimental diets, and was significantly higher for the diet with 10% seaweed inclusion. Rainbow trout fed with Porphyra meal presented a dark orange pigmentation of the flesh at the end of the trial, compared to the whitish color from the control fish. These results suggest that P. dioica can effectively be included in diets for rainbow trout up to 10% without significant negative effects on weight gain and growth performance. The pigmentation effect of the fish flesh by adding P. dioica meal to the feed is of a considerable interest to the organic salmon-farming industry.     

Growth of Nile tilapia (Oreochromis niloticus L.) fed with diets containing graded levels of green algae ulva meal (Ulva rigida) reared in geothermal waters of southern Tunisia

The use of green algae ulva meal (UM) (Ulva rigida) was evaluated as a replacement for soybean meal in a practical diet formulated to contain 28% crude protein, 7.50% lipid and 15 kJ gross energy g^?1. Soybean meal was replaced by 0%, 10%, 20% and 30% of UM (diets U₀, U₁, U₂ and U₃, respectively). The feeding experiment was carried out in an open circulation system. Each diet treatment was applied to triplicate groups of 30 fish (21.37 ± 0.193 g average wet weight) per tank (400 L) arranged in a completely randomized design. The fish were hand fed to satiation four times daily between 07.00 and 18.00 hours for 75 days. There were no significant differences (P > 0.05) in growth performance among fish fed with diets U₀, U₁ and U₂. However, fish fed diet U₃ had significantly lower growth (P < 0.05) than those fed diets U₀, U₁ and U₂. Fish fed the control diet (U₀) and diets including 10% and 20% UM had significantly (P < 0.05) better daily weight gain, relative growth weight, specific growth weight and protein efficiencies ratio than those fed with diet U₃. Feed conversion ratio increased with increasing UM content, but only the value found in fish fed with diet U₃ differed significantly (P < 0.05) from all other treatments. Survival rates ranged between 91.11% and 93.33%. No feed‐related mortality was observed during the entire experimental period. Apparent protein digestibility (APD) of diets ranged from 87.06 to 69.91% and was lowest for fish fed with diet U₃. In general, APD values decreased with increasing inclusion levels of UM, explained by the increase of anti‐nutritional factors and high non‐digestible fibre content. Compared to the control diet (U₀), fish fed diets containing high levels of UM had lower levels of carcass lipid and higher levels of carcass moisture. Results show that this product can be included by up to 20% in practical male Nile tilapia diets with no detrimental effects.     

Effect of some common West African farm-made feeds on the oxygen consumption and ammonia excretion rates of Nile tilapia,Oreochromis niloticus

The effects of two common West African farm-made feeds on postprandial metabolism were assessed in adult Nile tilapia (Oreochromis niloticus) by quantifying the oxygen consumption rates (MO₂) and total ammonia-nitrogen (TAN) excretion over a 24-h period. Measurements followed the ingestion of a single meal of a fishmeal-based control diet and two diets containing 30% copra (CM) or palm kernel meal (PKM) inclusions by groups of 15 adult O. niloticus per tank. The mean net MO₂ (postprandial oxygen consumption corrected for routine metabolic rate) during digestion for the different tilapia groups varied narrowly between 112.2 ± 9.9 and 129.9 ± 20.4 mg O₂ kg^?1 h^?1 with the fish fed the CM diet recording a significantly lower (p = 0.04) net MO₂ response relative to the other two diets. Net TAN excretion rates of the different dietary groups varied between 3.4 ± 1.4 and 4.4 ± 1.6 mg TAN kg^?1 h^?1. Under the standardized experimental conditions, copra and PKMs appeared to be promising candidates as partial replacements to fishmeal in tilapia diets as far as rates of oxygen consumption and ammonia-nitrogen excretion are concerned.     

Evaluation of Nutritive Value of Raw and Fermented De-oiled Physic Nut, Jatropha curcas Seed Meal in the Formulated Diets for Rohu, Labeo rohita (Hamilton) Fingerlings

Rohu (Labeo rohita) fingerlings, were fed de-oiled Jatropha curcas seed meal (DJSM) supplemented diets for 60 days and the effectiveness, if any, on the growth was evaluated. Nine isonitrogenous (35 % crude protein) and isocaloric (4.0 kcal g^?1) diets were formulated of which one was reference diet (RD, fishmeal based control diet) and the other eight were experimental diets prepared by incorporating raw (D1–D4) and fermented (D5–D8) DJSM at 10, 20, 30 and 40 % levels by weight, respectively. Autoclaved DJSM was processed through solid state fermentation (SSF) for 15 days at 37 ± 1 °C by an exo-enzyme producing bacterium, Bacillus cereus Lr.H.23 isolated from the hindgut of rohu, L. rohita. Processing through SSF caused decrease in the contents of crude fibre and anti-nutritional factors, but increase in the levels of free amino acids and free fatty acids. In terms of growth performance, feed utilization efficiency and apparent protein digestibility, fish fed diet D7 containing 30 % fermented DJSM showed the best performance, which differed significantly (P < 0.05) from that of the fish fed diets containing raw DJSM. The results indicated that an inclusion level up to 30 % fermented DJSM replacing 15 % FM in the practical diet for rohu fingerlings can be proposed when compared to the RD. However, further experiments are required to recommend the ingredient for use in industry.     

Growth performance and body composition in response to dietary protein and lipid levels in Nile tilapia (Oreochromis niloticus Linnaeus, 1758) subjected to normal and temporally restricted feeding regimes

A factorial experiment was designed to examine the effect on compensatory growth (CG) of Nile tilapia Oreochromis niloticus fed diets containing different protein and lipid levels under normal and temporally restricted feeding regimes. Four diets were formulated to contain either 30% or 36% crude protein, and 5% or 11% crude lipid. Triplicate replicates of each treatment were assigned to 24 150‐L tanks (20 fish/tank density). Fish (mean initial weight ± SD = 8.79 ± 0.34 g) were then fed either the normal feeding regime (thrice daily to apparent satiation) or the restricted regime (1 day feed deprivation followed by 3 days of feeding to apparent satiation) over a 44‐days study period. Fish receiving a diet under the restricted regime achieved weight gains (WG) comparable to fish consuming the diet containing 30% protein and 5% lipids under the normal feeding regime. Fish maintained on the restricted feeding regime exhibited reduced feed intake (FI), WG, feed efficiency ratio (FE), protein efficiency rate (PER) and hepatosomatic index versus fish on the normal feeding regime, except WG in fish fed the diet with 30% protein and 5% lipids. However, the resultant FI (85%~94%) was higher than the excepted 75% intake when fish were subjected to the restricted regime. Feeding 11% lipid diets led to improved FI, WG, FE, and PER compared to feeding the 5% lipid diets. Increased FI, WG, and FE, but reduced PER were observed in fish fed with 36% protein versus fish fed 30% protein. Fish receiving the 36% protein diets had lower whole‐body moisture and ash contents, but elevated whole‐body protein and lipid contents compared to those receiving the 30% protein diets. Whole‐body moisture contents were lower, but whole‐body protein, lipid and ash contents were higher in fish fed 11% lipid diets than in fish fed 5% lipid diets. There was an increase in whole‐body moisture content, but a decrease in protein and lipid content in response to the restricted feeding regime. Ash content was not affected by the feeding regime. The present study shows that Nile tilapia fed diets subjected to a restricted feeding regime exhibited growth comparable to those fed the diet at 30% protein and 5% lipid levels under a normal feeding regime. This positive effect was more pronounced in diets at a high protein level or in a combination of high protein and lipid levels.     

Dietary lipid sources affect cold tolerance of Nile tilapia (Oreochromis niloticus)

This study was carried out to evaluate the effects of dietary lipid sources on growth performance, fatty acids composition and cold tolerance of Nile tilapia (Oreochromis niloticus) fingerlings (7.00 ± 0.50 g/fish). The fish were fed four isonitrogenous (28% crude protein), isocaloric (500 kcal/100 g) diets containing four lipid sources; fish oil (FO), corn oil (CO), coconut oil (COCO) or fish oil/ corn oil mixture (1:1 ratio) (oil mix). The diets were offered to the fish at a daily rate of 3% of their body weights (BW), twice a day for two months. After the feeding trial, the fish were exposed to decreasing water temperature from 25 °C until the appearance of death symptoms. The results revealed that FO-based diets (FO and oil mix) produced the best growth rates and feed efficiency, followed by corn oil diet, while COCO resulted in the lowest performance. Fish fed on CO and oil mix showed higher body unsaturated fatty acids (UFA) and lower lethal temperature than those fed on FO- or COCO-based diets. These results indicate that cold shock can modify the lipid metabolism in Nile tilapia by lowering total body saturated fatty acids and raising n-6 and n-3 UFA. This finding suggests that the inclusion of high levels of plant oils in Nile tilapia feeds can enhance their cold tolerance.     

Effects of dietary lipid source on reproductive performance and tissue lipid levels of Nile tilapia Oreochromis niloticus (Linnaeus) broodstock

Nile tilapia were fed diets supplemented with one of the following lipid sources at 5% level: cod liver oil, corn oil, soybean oil, a coconut oil-based cooking oil or a combination of cod liver oil and corn oil (1 : 1). The control diet had no lipid supplement and tad fish meal as a sole protein source. A diet with soybean meal as a protein source was also tested. The number of females that spawned, spawning frequency, number of fry per spawning, and total fry production were increased at varying degrees by the supplemental lipid sources except for the cod liver oil. Fish fed the soybean oil diet tad the best overall reproductive performance over a 24-week period. Fish fed the cod liver oil diet had the highest weight gain but the poorest reproductive performance. The suplemental lipids significantly increased crude fat levels in the liver and ovaries. Both males and females Ld the cod liver oil diet had the highest levels of fat in the liver and muscle. The ratio of total n-6/n-3 fatty acid in the liver, ovaries and testes was influenced by the supplemental lipid sources. It was highest in fish fed either the soybean oil diet, the corn oil diet, or the soybean meal diet and lowest in fish fed the control diet or the cod liver oil diet.     

Gene expression,enzyme activity and performance of Nile tilapia larvae fed with diets of different CP levels

Protein is the most costly nutrient in fish feed, and while diets offered in the early stages of development typically have high levels of CP, they do not always correspond to the real requirements of the animals. Thus, research that seeks to learn the true nutritional requirements of fish is fundamental to improving commercial fish culture. The present study evaluated the protein requirements of Nile tilapia (Oreochromis niloticus) under larviculture. Fish performance, gene expression for digestive enzymes and their enzymatic activity and stress response to air exposure were analyzed. Four experimental diets differing in CP level were formulated: 30%, 36%, 42% and 48%. Fish larvae were fed the experimental diets during development and sampled 10, 20 and 30 days after the beginning of the experiment for performance, gene expression and enzymatic activity. At sampling time 30, stress resistance was also evaluated by means of an air exposure test. At sampling time 10, CP levels between 36% and 48% could be used for a better performance. During this period, pepsinogen expression was greater for 30% CP, intermediate for 42% and lower for 36% and 48%. After this initial period, diets of between 30% and 42% CP are recommended for better performance. At sampling time 20, gene expression for digestive enzymes and their enzymatic activity were similar for all diets tested. At sampling time 30, the diet of 42% CP induced both greater pepsinogen expression and pepsin activity. Survival after the air exposure test after 30 days of feeding was influenced by CP level in the diet, with the highest survival being for fish fed with 36% CP. Taken together, the present results demonstrate that dietary CP influences digestive enzyme gene expression and activity, and suggest that the best CP levels for Nile tilapia larviculture vary depending on larval stage.     

植酸酶对草鱼和新吉富罗非鱼消化酶活性的影响

植酸酶能水解植酸络合物,释放被植酸束缚的各种营养因子,因此能有效解除植酸与内源性消化酶的结合,促进消化酶的作用。本实验在全植物性饲料中添加植酸酶,研究其对草鱼(Ctenopharyngodon idellus)和新吉富罗非鱼(Oreochromis niloticus)淀粉酶及蛋白酶比活力的影响。以全植物性饲料为阴性对照组,添加磷酸氢钙(dibasic calcium phosphate,DCP)实验组为阳性对照组,另设4个不同梯度的植酸酶实验组(250 U/kg、500 U/kg、1 000 U/kg和2 000 U/kg)。实验选取健壮、规格齐整平均体质量为(12.59±0.09)g的草鱼和平均体质量为(9.59±0.12)g的新吉富罗非鱼,分别随机分为6个组,每组5个平行,每个平行20尾鱼。养殖8周后,草鱼平均体质量(18.29±0.63)g,新吉富罗非鱼平均体质量为(24.68±1.34)g,抽样取出胃、肠和肝胰脏用来分析淀粉酶和蛋白酶比活力。结果表明,植酸酶对无胃鱼草鱼和有胃鱼罗非鱼淀粉酶及蛋白酶比活力都有显著的促进作用。相比较而言,植酸酶对罗非鱼的应用效果较明显,低剂量就能显著提高其淀粉酶及蛋白酶比活力(P<0.05)。当植酸酶添加量达到1 000 U/kg时,草鱼和罗非鱼淀粉酶及蛋白酶比活力均达到峰值,此时,罗非鱼淀粉酶和蛋白酶比活力与阳性对照组无显著差异(P>0.05),而草鱼肝胰脏蛋白酶比活力显著高于阳性对照组(P<0.05)。植酸酶2 000 U/kg实验组,罗非鱼淀粉酶和蛋白酶比活力与1 000 U/kg植酸酶实验组无显著差异(P>0.05),但草鱼肝胰脏蛋白酶比活力显著低于1 000 U/kg植酸酶实验组(P<0.05)。因此,本实验条件下,植酸酶在草鱼和新吉富罗非鱼全植物性蛋白质配合饲料中的适宜添加量均为1 000 U/kg,生产实践中可通过添加植酸酶部分替代无机磷源。     

Potential use of green macroalgae Ulva lactuca as a feed supplement in diets on growth performance,feed utilization and body composition of the African catfish,Clarias gariepinus

This study aimed to evaluate the effects of diet containing the green macroalgae, Ulva lactuca, on the growth performance, feed utilization and body composition of African catfish Clarias gariepinus. Four experimental diets were formulated: D1 as a control group and D2, D3 and D4 which included 10%, 20% and 30% U. lactuca meal, respectively. 180 African catfish, weighing 9.59 ± 0.43 g, and with an average length of 11.26 ± 0.21, (mean ± SE) were divided into four groups corresponding to the different feeding regimes. The final body weight of the fish showed insignificant differences (P > 0.05) between the control and fish fed D2, whereas, there was a significant difference (P < 0.05) between these two diets compared with D3 and D4, with weights of 70.52, 60.92, 40.57 and 35.66 g recorded for D1, D2, D3 and D4, respectively. In the same trend significant differences were also evident in weight gain, specific growth rate and feed utilization. Fish fed with a diet containing 20% or 30% U. lactuca meal had poorer growth performance and feed utilization. Protein productive value, protein efficiency ratio, daily dry feed intake and total feed intake were also significantly lower in fish fed with D3 and D4 than in the control D1 and D2.Overall, the results of the experiment revealed that African catfish fed a diet with U. lactuca included at 20% and 30% levels showed poorer growth and feed utilization than the control group and fish fed diets containing 10% of U. lactuca.     

Effects of Different Sources and Levels of Copper on Growth Performance,Nutrient Digestibility,and Elemental Balance in Young Female Mink (Mustela vison)

An experiment was conducted in a 3?×?3?+?1 factorial experiment based on a completely randomized design to evaluate the effects of different sources of copper on growth performance, nutrient digestibility and elemental balance in young female mink on a corn–fishmeal-based diet. Animals in the control group were fed a basal diet (containing 8.05 mg Cu/kg DM; control), which mainly consisted of corn, fish meal, meat bone meal, and soybean oil, with no copper supplementation. Minks in other nine treatments were fed basal diets supplemented with Cu from reagent-grade copper sulfate, tribasic copper chloride (TBCC) and copper methionate. Cu concentrations of experiment diets were 10, 25, and 40 mg/kg copper. A metabolism trial of 4 days was conducted during the last week of experimental feeding. Final body weight and average daily gain increased (linear and quadratic, P?<?0.05) as Cu increased in the diet; maximal growth was seen in the Cu25 group. Cu supplementation slightly improved the feed conversion rate (P?=?0.095). Apparent fat digestibility was increased by copper level (P?=?0.020). Retention nitrogen was increased by copper level (linear, P?=?0.003). Copper source had a significant effect on copper retention with Cu-Met and copper sulfate treatments retention more than TBCC treatments (P?<?0.05). Our results indicate that mink can efficiently utilize added dietary fat and that Cu plays an important role in the digestion of dietary fat in mink, and mink can efficiently utilize Cu-Met and CuSO₄.     

Nutrient digestibility and intestinal enzyme activity of Clarias batrachus (Linn.) juveniles fed on dried fish and chicken viscera incorporated diets

A feeding trial was conducted for 56 days to study the effect of replacement of fish meal by dried fish and chicken viscera, and a combination of oil cakes, in the diet of Clarias batrachus juveniles. The nutritional values of these by-products were studied through a digestibility experiment. No significant difference in nutrient digestibility was observed in different diets. Even 19.59% lipid in the diet of catfish did not affect the nutrient digestibility. Both amylolytic and proteolytic enzymes in the intestine of juveniles were studied. A decreased protease activity due to replacement of animal protein by plant protein and a decreased (P < 0.01) aspartate aminotransferase (ASAT) activity could be observed after inclusion of 22% of dried fish viscera in the diet of the catfish. Though body lipid content increased in fish fed a high level of lipid, fat-free body composition did not vary among the fish fed on different diets.     

Replacement value of hatchery waste meal for fish meal in layer diets

An experiment was conducted in which hatchery waste meal (HWM) replaced fish meal (protein for protein) in layer diets at 0%, 33%, 66% and 100% levels. Both feed and protein intake were superior on HWM diets. The highest hen-day production of 73.97% was obtained on diet 2 in which 33% of fish meal was replaced with HWM. Egg weight and egg length were also superior on HWM diets. All birds fed on HWM diets had thicker egg shells (0.33 mm) than did those fed on the control diet, fish meal diet (0.32 mm). Results obtained for yolk weight were statistically different (P < 0.05). Highest values for yolk weight (16.91 g) and albumen weight (40.93 g) were recorded for birds fed with diet 4 in which 100% fish meal was replaced with HWM. HWM can replace fish meal completely in layer diets without adverse effect on egg quality characteristics.