Artificial spawning of female Lithuanian strain B carp (Cyprinus carpio L.) after treatment with carp pituitary homogenate, Ovopel or [d-Tle6, ProNHEt9] GnRH-a (Lecirelin)

The results of reproduction of females from Lithuanian strain B carp after ovulation stimulation with carp pituitary homogenate (CPH; 0.3+2.7 mg kg^?1; group I), Ovopel (1/5+1 pellet kg^?1; group II) or [d ‐Tle⁶, ProNHEt⁹] GnRH‐a (Lecirelin) with metoclopramide (15 μg kg^?1+10 mg kg^?1 respectively; group III) were investigated. The lowest percentage of spawning females (71%) was recorded in the group treated with CPH. In case of Ovopel or Lecirelin induced ovulation, 86% of females spawned. No statistically significant effect of the ovulation stimulator (group) on the weight of eggs was found; however, the highest mean weight of eggs (expressed both in grams and in the percentage of female body weight) was recorded for the group treated with Ovopel (1400 g and 13%). After the treatment with CPH or Lecirelin, the weight of eggs was 1140 g (11%) and 1100 g (10%) respectively. The ovulation stimulator significantly affected the percentage of live embryos after 36 and 48 h incubation of eggs (P≤0.05; P≤0.01). After treatment with [d ‐Tle⁶, ProNHEt⁹] GnRH‐a, eggs of the best quality were obtained and after 36 and 48 h incubation the mean percentages of live embryos were significantly higher than the means calculated for the remaining two groups. No statistically significant differences were found between the percentage of living embryos after 36 and 48 h incubation of groups I and II.     

Artificial spawning of carp, Cyprinus carpio (L.)

The effect of reproduction was investigated on females of Hungarian strain W, French strain F, and their cross‐breed 1X whose ovulation was stimulated with carp pituitary (0.3 mg kg^?1and, after 12 h, 2.7 mg kg^?1) or Ovopel (one‐fifth of a pellet per kg and, after 12 h, one pellet per kg). It was found that in the case of Ovopel treatment, the percentage of spawning females of strain F and the cross‐breed 1X was higher than in the hypophysed fish compared. The applied ovulation stimulators did not significantly affect the weight of obtained eggs, whereas the significant (P ≤ 0.01) effect was recorded with respect to the quality of eggs after 12‐, 24‐, 36‐ and 48‐h of incubation. After Ovopel stimulation, the quality of eggs was better. The origin of the females had no statistically significant effect on the weight of eggs although the yield of eggs from fish of strain W was much smaller than that from females of strain F and the 1X cross‐breed. The interaction between the ovulation stimulator and the provenance of the females was significant (P ≤ 0.05) for the percentage of live embryos after 48‐h of incubation of eggs. Eggs of the best quality (and highest weight) were obtained from fish of strain F and cross‐breed 1X treated with Ovopel. In females of strain F that spawned within 6 and 10 h after the second Ovopel injection, the effect of the ovulation time on the weight of eggs was non‐significant. It was significant with respect to the percentage of egg fertilization and of live embryos after 36‐h of incubation (P ≤ 0.01 and P ≤ 0.05 respectively). The better quality of eggs (and their higher weight) was recorded when this time was shorter.     

Artificial spawning of carp Cyprinus carpio L.: differences between the effects on reproduction in females of Polish and Hungarian provenance treated with carp pituitary and (D-Ala6) GnRH ProNHEt (Kobarelin)

Ovulation was stimulated in carp females of Polish and Hungarian provenance using injections of ( d ‐Ala⁶) GnRH ProNHEt (Kobarelin) (20 μg kg^?1) with metoclopramide (10 mg kg^?1) or carp pituitary (3 mg kg^?1). For estimating the effects of the substance stimulating ovulation and of the female provenance, analysis of variance was carried out using the least squares method. It was found that the stimulating substance, provenance and interaction of these factors did not significantly affect the weight of eggs obtained. On the other hand, the stimulating substance, provenance and interaction had a highly significant (P ⩽ 0.0001) effect on the percentages of fertilization and live embryos. Females of Hungarian provenance treated with Kobarelin yielded eggs of much better quality but a smaller weight than after the pituitary treatment. In the case of carp females of Polish provenance, a yield of eggs of smaller weight and very poor quality was noted compared with the weight and quality of eggs obtained after hypophysation.     

Artificial spawning of African catfish Heterobranchus longifilis: differences between the effects on reproduction in females treated with carp pituitary homogenate or Ovopel

The effects of the controlled reproduction of African catfish Heterobranchus longifilis after ovulation stimulation with carp pituitary homogenate (CPH; 4 mg kg^?1; group I) or Ovopel (1/5+1 pellet kg^?1; group II) were investigated. After the application of Ovopel, eggs were obtained from a higher percentage of females than after a CPH treatment (87.5% and 75.0% respectively). The statistically significant (P≤0.05) effect of ovulation stimulator was specified only in the case of the weight of eggs (expressed in grams and in percentage of female body weight), being higher in fish treated with Ovopel compared with CPH‐treated fish (176.02 g, 8.43% and 109.51 g, 5.48%). The quality of eggs expressed in percentage of live embryos after 24 h incubation was higher by 7.5% in fish treated with Ovopel. Latency period did not significantly affect the weight of eggs, fertilization percentage or percentage of living embryos after 24 h of egg incubation. However, the weight of eggs and percentage of living embryos after 24 h incubation were higher in fish spawning after 12 h latency (159.38 g and 85.30%) compared with the weight and quality of eggs obtained from females spawning after 14 h latency (126.15 g and 76.04%).     

Artificial spawning of female Polish line 3 carp (Cyprinus carpio L.) after treatment with pituitary homogenate and/or Ovopel

Stimulation of ovulation was carried out in female carp (Cyprinus carpio L.) of Polish line 3, with carp pituitary homogenate, Ovopel (the preparation contains d ‐Ala⁶, Pro⁹NEt‐mGnRH and metoclopramide), and Ovopel and carp pituitary homogenate. The effect of the ovulation stimulators on the weight of eggs expressed in grams and as a percentage of female body weight was determined. The effect of the treatments on the quality of eggs expressed as the percentage of living embryos after 24‐ and 36‐h incubation was also determined. The best results were obtained after stimulation with Ovopel (the priming dose) and pituitary homogenate (the resolving dose). In this case all the females spawned, and the highest yield and quality of eggs were recorded. The poorest results were noted if the ovulation was stimulated with repeated injection of carp pituitary homogenate. The females treated with carp pituitary homogenate gave eggs of poorer quality than those stimulated with two doses of Ovopel or with Ovopel and pituitary homogenate. The percentage of living embryos after 24‐ and 36‐h incubation of eggs was significantly higher for the group stimulated with Ovopel and pituitary homogenate than for the other treatments.     

Artificial spawning of carp (Cyprinus carpio L.): differences between females of Polish strain 6 and Hungarian strain W treated with carp pituitary homogenate, Ovopel or Dagin

Investigations of the effects of controlled reproduction were conducted on carp females of Polish strain 6 and Hungarian strain W after ovulation stimulation with carp pituitary homogenate (CPH) (0.3 mg+2.7 mg kg^?1 body weight), Ovopel (1/5+1 pellet kg^?1 body weight) or Dagin (1 dose kg^?1 body weight). In both strains, the highest percentage of spawning females was found after the Ovopel treatment. After treatments with CPH and Dagin this percentage did not differ in strain 6; however, after Dagin, it was higher in fish of strain W. After CPH or Ovopel stimulation the females of line 6 yielded eggs of higher weight compared with line W. After the Dagin treatment the weight of eggs obtained from females, both strains was similar but much lower than after the two remaining agents. The quality of eggs expressed both by the percentage of fertilization and that of living embryos after 24 and 36 h incubation was similar in the two strains only in the group treated with Ovopel. After CPH application eggs of better quality were obtained from strain 6 compared with strain W; however, after the treatment with Ovopel, eggs of much better quality were noted in strain W. In general, the best effects of reproduction were recorded in the case of Ovopel and the poorest in that of Dagin. Females of strain 6 yielded eggs of a higher weight but the percentages of spawning females were higher in strain W after each of the applied spawning agents. A new approach to this problem consisted in investigating the interaction between ovulation stimulators and origin of females of fish treated with Dagin.     

Induction of ovulation in ornamental common carp (Koi, Cyprinus carpio L.) using LHRHa ([d-Ser(tBu)6, Pro9-NEt]-LHRH) combined with haloperidol and carp pituitary extract

The effects of a single injection of mammalian superactive analogue [d ‐Ser(tBu)⁶,Pro⁹‐NEt]‐LHRHa (20 μg/ kg^?1) combined with the dopamine antagonist, haloperidol (HAL, 0.5 mg kg^?1), for induction of ovulation in the koi carp broodstocks were determined under routine hatchery conditions. The results were compared with classic carp pituitary extract (CPE, double injection) application (water temperature 22 °C). Physiological saline (0.7% NaCl)‐injected fish were used as a control group and no ovulation occurred in this group. The spawning ratio was high in the LHRHa+HAL treatment group and in the CPE treatment group (6/7 and 5/7 respectively). The latency period was 14–16 h in the LHRHa+HAL treatment group and 12–14 h in the CPE treatment group (after the second injection). There was no difference between the two ovulating groups with respect to the spawning index (the weight of eggs as a percentage of female body weight) and fertilization rate of eggs (P>0.05). As a result, ovulation can be induced successfully in koi carp broodstocks with 20 μg kg^?1 [d ‐Ser(tBu)⁶,Pro⁹‐NEt]‐LHRHa+0.5 mg kg^?1 HAL treatment in a single injection without decreasing the egg quality. Application of this combination can be useful for hatchery and broodstock management in koi carp culture.     

Artificial spawning of carp (Cyprinus carpio L.): the use of Aquaspawn and carp pituitary to induce ovulation in females of Lithuanian line B

Ovulation stimulation was carried out in carp (Cyprinus carpio L.) females of Lithuanian line B, using carp pituitary (0.3 + 2.7 mg kg^?1), Aquaspawn (0.5 mL kg^?1) and Aquaspawn + carp pituitary (0.3 mL kg^?1 + 2.7 mg kg^?1). The poorest results of reproduction (the lowest percentage of ovulating females, the lowest weight of eggs and their poorest quality) were obtained after double hypophysation. The best results were induced by the application of Aquaspawn alone. The effect of the applied stimulators was statistically non‐significant with respect to the weight of eggs, being highly significant (P ≤ 0.01) with respect to the percentage of fertilized eggs and that of living embryos after 24‐ and 36‐h incubation. The multiple‐regression equations were calculated for the three groups separately. The percentage of living embryos after 36‐h incubation constituted a dependent variable while the mass of females, the mass of eggs, the fertilization percentage and the percentage of living embryos after 24‐h incubation were independent variables. The regression was only significant (P ≤ 0.01) for the group of fish treated with Aquaspawn.     

Artificial spawning of European catfish Silurus glanis L.: differences between propagation results after stimulation of ovulation with carp pituitary and Ovopel

The effect of spawning on European catfish females with an average body weight of 5.6 kg and 11.2 kg was investigated, with carp pituitary and Ovopel being used as ovulation stimulators. Ovopel induced ovulation in a higher percentage of females of both smaller and larger body weight. The applied ovulation stimulators did not significantly affect the weight of the obtained eggs. On the other hand, the effect of the stimulators was highly significant (P≤ 0.01) with respect to the percentage of live embryos after 24‐, 48‐ and 56‐h incubation. The fish of greater body weight yielded eggs of a significantly (P≤ 0.05) greater weight, although of poorer quality. The interaction between the ovulation stimulator and female body weight was statistically significant (P≤ 0.05) for the weight of the obtained eggs and highly significant (P≤ 0.01) for the percentage of live embryos after 48‐h incubation. For the percentage of live embryos after 24‐ and 56‐h incubation, the statistical significance (P≤ 0.05) of this interaction was determined. In the case of females of smaller body weight, a statistically significant (P≤ 0.05) phenotypic correlation was found between the percentage of live embryos after 24‐h incubation and that after 48‐h incubation, and also between the percentage of live embryos after 24‐ and 56‐h incubation.     

Artificial spawning of carp Cyprinus carpio L.: differences between the effects on reproduction in females of Israeli strain Dor-70 and its cross-breed treated with carp pituitary and Ovopel

The effects on carp reproduction were investigated in females of the Dor-70 strain and a cross-breed of this line with a Hungarian one of carp pituitary and Ovopel as ovulation stimulators. It was clear that, in the case of the Ovopel treatment, a higher percentage of females spawned, although the weight of eggs obtained was less than that yielded by hypophysed fish, the differences being highly significant (P ≤ 0.01) with respect to the weight in grams and to percentage of female body weight. No statistically significant differences were determined in the quality of eggs, measured by both the fertilization percentage and the percentage of living embryos, obtained after the two stimulators were used. Neither the provenance of females nor the interaction of female provenance and the stimulator has any effect on the traits investigated. The correlation between the percentage of fertilization and the percentage of live embryos was 0.54 for strain Dor-70 and 0.95 for the cross-breed. The multiple regression equations were calculated for strain Dor-70 and for cross-breed 5 separately, where the percentage of living embryos constituted a dependent variable and the mass of a female, mass of eggs in grams and the percentage of fertilization were independent variables. We appraised the regressions as significant for Dor-70 (P ≤ 0.04) and highly significant for the cross-breed (P ≤ 0.0001).     

Induced spawning in bream, Abramis brama (L.), using carp and bream pituitary extract and hCG

Induced spawning in bream, Abramis brama (L), was studied using acetone-dried common carp pituitary (CP) and bream pituitary (BP) with or without the addition of human chorionic gonadotrophin (hCG). The total dose administered to fish was of 5.0 mg kg^?1 BP or 4.0 mg kg^?1 CP with or without 2000-2200 IU hCG kg^?1 for females and 2.5 mg kg^?1 BP or 2.0 mg kg^?1 CP with or without 1000–1100 IU HCG kg^?1 for males. In all male treated groups 100% of spermiation was observed: in females the most effective method was a triple injection with hCG and carp pituitary, resulting in 79% of females ovulated (over 68% of eyed eggs). Biological quality of eggs, expressed as a percentage of eyed eggs, was negatively correlated with time elapsing between resolving (final) injection and ovulation. Spawning success, expressed as a value of S_e (spawning effectiveness coefficient), was higher in fish treated with triple injection.     

Characteristics of the reproduction effectiveness of four Hungarian breeding lines of carp Cyprinus carpio (L.)

The effectiveness of reproduction of four Hungarian breeding lines 7, 8, W, and 0 of carp Cyprinus carpio was investigated. The highest percentage of ovulating females after Ovopel stimulation of ovulation (1/5 + 1 pellet kg^?1 BW of females) was found in line 8 (100 %), in line 0, it was 86.21 %, and in lines 7 and W, the respective values were 73.68 and 76.47 %. It was noted that the breeding line significantly (P ≤ 0.05) determined the weight of the eggs (expressed in grams and percentage of female BW), the fertilization percentage, the percentage of living embryos after 24- and 36-h incubation, the total number of eggs, and the number of live embryos after 36-h incubation. The highest weight of eggs was obtained from females of line 7 (1,083.41 g) and line 8 (981.54 g), while the lowest weight was noted in the case of females of line W (804.94 g). The highest number of eggs was found in line 7 (722,300) and in line 8 (654,400). For these lines, the highest number of live embryos (36 h) was also found (624,400 and 622,200, respectively). Within each line investigated, the regression equations were derived in order to predict the weight of eggs (g), percentage of live embryos, and the number of live embryos after 36-h incubation.     

Differences in the effectiveness of reproduction among ten breeding strains of the common carp Cyprinus carpio L. after stimulation of ovulation with carp pituitary homogenate or [(D‐Ala6, Pro9NEt) mGnRH‐a + metoclopramide] (Ovopel)

This study focused on the reproduction effectiveness of 10 breeding strains of common carp (Polish strains 2, 3, 6; Hungarian strains 0, W, 7; Lithuanian strain B; French strain F; Israeli strain D and Yugoslavian strain J) after stimulation of ovulation with carp pituitary homogenate or Ovopel. The percentage of females with recorded ovulation became higher after Ovopel treatment in as many as eight breeding strains (2, 3, 6, 0, W, B, F, D). The interaction between the spawning agent and the breeding strain was statistically significant (P ≤ 0.05) for the mass of spawn and non‐significant for traits determining the quality of eggs. Among the 10 breeding strains, in 4 (3, 7, B, J) the least‐squares means (LSM) for the weight of egg (g) were higher for fish stimulated with Ovopel. Among the strains tested, in seven (3, W, F, J, 2, 7, B), the LSM for the percentage of living embryos after 36 h incubation were higher for fish treated with Ovopel. The evaluation of reproduction effects based on the values of such parameters as the percentage of ovulating females, weight of eggs (g) and the percentage of live embryos (36 h) showed that after Ovopel treatment the poorer effects were obtained only for strains 6, 0 and D.     

Artificial spawning of European catfish, Silurus glanis L.: stimulation of ovulation using LHRH-a,Ovaprim and carp pituitary extract

Ovulation was stimulated in four groups of European catfish, Silurus glanis L., using injections of des-Gly¹⁰, [D-Ala⁶]-LHRH Ethylamide (20 μg kg^–1) and pimozide (10 mg kg^–1), Ovaprim (0.33 mL kg^–1), and carp pituitary extract (4 mg kg^–1, in one or two doses). A higher percentage of ovulating females (producing eggs of sufficient quality) was found after the LHRH-a and Ovaprim treatments (100% and 80%) in relation to fish treated with the pituitary extract (60% and 66.67%). The greatest weight of eggs was obtained in the case of repeated hypophysation and LHRH-a (1299.69 and 1298.57 g, respectively), and the smallest after single hypophysation (1144.08 g). After 60 h of incubation, the best quality of eggs was found in the group treated with Ovaprim (62.9% of live embryos) and the poorest in the two groups which underwent hypophysation (50.41% and 50.75%). No statistically significant effect by the ovulation stimulators on the characteristic qualitative and quantitative traits of obtained eggs was ascertained.     

Spawning induction in Kutum Rutilus frisii kutum (Kamenskii, 1901) using carp pituitary extract or GnRH analogue combined with metoclopramide

Kutum Rutilus frisii kutum (Kamenskii, 1901), Cyprinidae is an endemic fish of the Caspian Sea. Iranian Fisheries Organization (Shilat) produce up to 200 million fry (1–2 g body weight (b.w.)) to restock the Caspian Sea population annually. Some of these fry are produced by spawning induction in broodfish by carp pituitary extract (CPE). The objective of this study was to assay the effectiveness of the gonadotropin releasing hormone analogue (d ‐Ala⁶, Pro⁹‐Net GnRH) alone or in combination with metoclopramide (MET), a dopamine antagonist, on the percentage of ovulated females, latency period, ovulation index and fertilization success. The following hormone treatments were tested: single injection of 2 mg kg^?1 b.w. of CPE as a positive control, GnRHa alone 20 and 40 μg kg^?1 b.w. and combination of GnRHa and MET as follows: 5 μg+2.5 mg, 10 μg+ 5 mg and 20 μg+10 mg kg^?1 b.w. Negative control group was injected with 0.7% saline. The percentage of ovulated females, ovulation index and fertilization success were 90%, 71.3±1.24%, 68.4±2.3%, respectively, in the group treated with GnRHa+MET at a dose of 20 μg+10 mg kg^?1 b.w. and were significantly higher than those in the positive control (60%, 64.5±0.23%, 69.1±4.5%) (P<0.05). However, the latency period in this group was longer than that in the positive control (P<0.05). Only 20% and 40% fish ovulated in groups that received 20 or 40 μg kg^?1 b.w. GnRHa. No fish ovulated in the negative control.     

Artificial Spawning of African Catfish,Clarias gariepinus

Abstract

The effects of controlled reproduction of African catfish, Clarias gariepinuswere investigated in an experiment with carp pituitary (at the dose 4 mg/kg body weight) or Ovopel (1 pellet/kg body weight) used as ovulation stimulators. The application of the synthetic stimulator led to the significantly (P≤0.01) greater weight of eggs (expressed in grams and as percentage of female body weight) and to the significantly (P≤0.05) higher quality of eggs after 24-hour incubation as compared with the hypophysation effects. Two categories of females were used in the experiment, i.e., light (mean body weight of 3.75 kg) and heavy (mean body weight of 8.86 kg) fish. The results show that a significantly (P≤0.01) greater weight of eggs (expressed in grams) was obtained from heavier females. The quality of eggs expressed as the percentage of live embryos after 12- and 24-hour incubation was significantly (P≤0.01 and P≤0.05, respectively) higher for lighter females. The higher weight of obtained eggs and their better quality after Ovopel stimulation compared to the weight and quality of eggs obtained after hypophysation allow for the recommendation of this ovulation stimulator for the fish species investigated.     

Ovulation induction in jundiá (Rhamdia quelen,Heptapteridae) using carp pituitary extract or salmon GnRH analogue combined with dopamine receptor antagonists

Jundiá (Rhamdia quelen) is an important species for aquaculture in temperate and subtropical climates. In the present study, the results of different forms of GnRH analogue treatments on ovulation in jundiá have been compared with those from treatment with carp pituitary. Seven out of eight females ovulated in groups treated with carp pituitary (4.0 mg kg^?1 BW) and Ovaprim (0.5 mL kg^?1 BW). Injection with sGnRHa (10 μg kg^?1 BW) combined with metoclopramide (20 mg kg^?1 BW) caused a significantly lower rate of ovulation with three out of eight females responding. None of the fish injected with sGnRHa (10 μg kg^?1 BW) alone ovulated. Mean PGSI [(weight of stripped egg mass/BW of the female before stripping) × 100] and mean fertilization rate values were high and similar between treatment groups. The obtained results indicate that in jundiá, there is a strong dopamine inhibitory tone on gonadotropin secretion. The gonadotropin releasing activity of sGnRHa can be potentiated by dopamine receptor antagonists and the combined treatment is effective in inducing ovulation. In this regard, domperidone proved to be more potent than metoclopramide.     

LHRHa‐induced ovulation of the endangered‐Caspian brown trout (Salmo trutta caspius) and its effect on egg quality and two sex steroids: testosterone and 17α‐hydroxyprogestrone

To induce synchronized ovulation, migrating wild Caspian brown trout (Salmo trutta caspius) females were treated with two interperitoneal injections of Des‐Gly¹⁰, d ‐Ala⁶ LHRH (LHRHa), given 3 days apart. Two injections of 100 μg kg^?1 body weight of this hormone effectively induced ovulation. Within 27 days from the second injection, all fish injected with 100 μg kg^?1 LHRHa had ovulated compared with 54.5% of the controls. The mean time to ovulation was reduced significantly (P<0.05) from 31.67±4.84 days in control fish and 28.83±7.31 days in sham‐treated fish to 16.36±1.61 days in fish injected with 100 μg kg^?1 LHRHa. The fertilization rate in 50 and 100 μg kg^?1 LHRHa‐injected fish was significantly lower than that in the control fish (P<0.05). In fish injected with 50 and 100 μg kg^?1 LHRHa, significant (P<0.05) changes in testosterone (T) and 17α‐hydroxyprogestrone (OHP) levels were observed. After the second LHRHa injection, the fish injected with 100 μg kg^?1 showed the highest serum levels of testosterone and OHP. These results demonstrate that the use of LHRHa can effectively reduce the mean time to ovulation and induce synchronized ovulation in Caspian brown trout.     

Effects of dietary protein and lipid levels and DP DE−1 ratio on growth, feed utilization and hepatosomatic index of juvenile haddock, Melanogrammus aeglefinus L.

Juvenile haddock, Melanogrammus aeglefinus L. (initial weight, 13.5 ± 0.1 g) were fed practical diets containing digestible protein to digestible energy (DP DE^?1) ratios of 25–30 g DP MJ DE^?1as‐fed using three protein levels (450, 500 and 550 g kg^?1) each at two lipid levels (110 and 160 g kg^?1) for 63 days. The results showed mean weight gain and feed conversion ratio were highest for diets containing 28.5 and 30.2 g DP MJ DE^?1. DP DE^?1 ratio had no significant effect on protein efficiency ratio except at the lowest level (24.7 g DP MJ DE^?1) indicating a protein sparing effect of higher lipid when dietary protein is below the requirement. Haddock appears to preferentially use protein as the prime source of DE. DP DE^?1 ratio had little effect on apparent digestibility (AD) of protein while AD of lipid was significantly affected. Significant differences in AD of energy and organic matter were found to be inversely related to the carbohydrate level of the diet. DP DE^?1 ratios of 28.5 g DP MJ DE^?1 or lower resulted in significantly higher hepatosomatic indexes. The highest whole‐body nitrogen gains and energy retention efficiencies were achieved at 28.5 and 30.2 g DP MJ DE^?1, whereas only slight differences in nitrogen retention efficiencies were observed. The highest levels of energy retained in the form of protein were achieved at 28.5 and 30.2 g DP MJ DE^?1. The diet that provided the best growth, feed utilization and digestibility with minimal HSI contained 546 g kg^?1 protein (513 g kg^?1 DP), 114 g kg^?1 lipid, 164 g kg^?1 carbohydrate, 17.0 MJ kg DE^?1 and a DP DE^?1 ratio of 30.2 g DP MJ DE^?1.     

Dietary histidine requirement of fingerling Indian major carp, Cirrhinus mrigala (Hamilton)

An 8‐week growth trial was conducted to determine the dietary histidine requirement of the Indian major carp, Cirrhinus mrigala fingerling (length 4.22 ± 0.45 cm; weight 0.61 ± 0.08 g; n = 40). Isonitrogenous (400 g kg^?1 crude protein) and isoenergetic (17.90 kJ g^?1 gross energy) diets with graded levels of l ‐histidine (2.5, 5.0, 7.5, 10.0, 12.5 and 15.0 g kg^?1 dry diet) were formulated using casein and gelatin as a source of intact protein, supplemented with l ‐crystalline amino acids. Twenty fish were randomly stocked in 70‐L indoor polyvinyl circular fish tank (water volume 55‐L, water exchange rate 1–1.5 L min^?1) and fed experimental diets at the rate of 5% of their body weight/day divided over two feedings at 08:00 and 16:00 h. Maximum live weight gain (295%), best feed conversion ratio (FCR) (1.48) and protein efficiency ratio (PER) (1.69) occurred at 7.5 g kg^?1 of dietary histidine level. When live weight gain, FCR and PER data were analysed using second‐degree polynomial regression, the break points indicated histidine requirements at 9.4, 8.6 and 8.5 g kg^?1 of dry diet respectively. Significantly (P < 0.05) higher whole body protein and low moisture values were recorded at 7.5 g kg^?1 histidine level. Body fat increased significantly (P < 0.05) with increasing histidine levels. However, at 7.5 and 10 g kg^?1 histidine diets body fat did not differ (P > 0.05) to each other. Ash content of fish fed diets containing various levels of histidine did not differ except at 2.5 and 5.0 g kg^?1 inclusion levels where significantly (P < 0.05) higher ash was recorded. Protein deposition was also found to be significantly (P < 0.05) higher in the 7.5 g kg^?1 histidine diet. Based on the polynomial regression analysis of FCR and PER data, it is recommended that the diet for fingerling C. mrigala should contain histidine at 8.5 g kg^?1 of dry diet, corresponding to 21.25 g kg^?1 of dietary protein for optimum growth and efficient utilization of feed.