The present study investigated the effects of phytoadditive carvacrol on growth performance, feed utilization, hematological, non-specific immune and serum biochemical parameters in rainbow trout ( Oncorhynchus mykiss). In trial, 240 rainbow trout which had average weight of 10.79 ± 0.57 was used. Fish were divided into four groups before being fed for 60 days with 0, 1 (C1), 3 (C3) or 5 (C5) g/kg of carvacrol. There were no particular differences in the growth performance, feed utilization, whole body composition, hematological parameters between the experimental group and the control group. However, as compared to control group, a significant increase of serum lysozyme activity was seen in groups receiving feed containing C3 and C5 groups after 30 days. The myeloperoxidase activity in groups (C1 and C3) was significantly higher on the 30th day of sampling. Myeloperoxidase activity of C5 treated group was significantly higher on the 60th day in comparison with the control group. Serum glucose levels significantly decreased on 60th day for C1, C3 and C5 treated groups. The serum total protein, globulin and triglyceride levels of C3 treated groups was significantly higher on the 60th day in comparison with the control and other carvacrol treated groups. The level of serum cholesterol in C5 treated groups was significantly lower on the 30th day in comparison with the control and other carvacrol treated groups. The results of the present study indicated that dietary supplementation of 3 g/kg of carvacrol in commercial diets could improve some non-specific and biochemical status in rainbow trout.
Aquaculture industry has shown a rapid growth in recent years. The main aims of industry area is both increasing growth rates of fish and protecting their health. Antibiotics have been used for promoting growth and struggling with illness for a long time. However, use of antibiotics in fish aquaculture have been limited and prohibited in many countries [
Especially herbs or essential oils of herbs can be used for struggling against pathogen bacterias with its antimicrobial and antioxidant features. The features of herbals can be related to terpenoid and phenolic compounds [
Carvacrol is a major component of oregano and thyme essential oils. It is recognized as a safe component by the U.S. Food and Drug Administration (2010), by the Council of Europe (2000), and FAO/WHO Committee on Food Additives (2001). Some studies have reported that oral administration of combination of carvacrol and thymol in Ictalurus punctatus [
Trial was applied in commercial trout farm (Çobanlar) in Fethiye. In trial, 12 polyester tanks (3 × 0.8 × 0.4 m) consisted of 480 liter were used. Trial was carried out in continuous flow system and water was exchanged daily 6 - 8 times. In trial, 240 rainbow trout (O. mykiss) which has average weight of ±SD = 10.79 ± 0.57 was used. Fish were fed by hand 2 times a day in the ratio of % 2 of their body weight during 60 days trial. Water temperature, dissolved oxygen, pH and EC (electrical conductivity) were measured at 7˚C, 5.72 mg∙L−1, 8.04, 1408 µmhos/cm.
Carvacrol (W224502, Sigma-Aldrich, Munich, Germany) was added to a commercial trout extruder feed (Çamlı Feed Company, Turkey,
Growth performance of rainbow trout with different diets was considered by calculating weight gain (WG), specific growth rate (SGR), feed conversion rate (FCR) and death rate.
Chemical Analyses | |
---|---|
Crude Protein (%) | 49 |
Crude Lipid (%) | 19 |
Crude Cellulose (%) | 3 |
Crude Ash (%) | 13 |
Energy (kcal/kg) | 4329 |
Amino Acids (%) | |
Lysine | 4.7 |
Methionine + Cystine | 2.4 |
Vitamins (per kg Feed) | |
A (IU) | 2500 |
D3 (IU) | 3050 |
E (mg) | 240 |
K (mg) | 10 |
C (mg) | 250 |
Macro Elements (%) | |
Calcium | 1-2 |
Total Phosphor | 1.5 |
Sodium | 0.2/1 |
Ingredients: fish meal, fish oil, soybean and by products, wheat and by products, yeast and by products, amino acids, vitamins and minerals.
Proximate analyses of the diets were performed using standard methods [
Blood samples of six fish/groups were collected randomly from the caudal vein using a vacutainer fitted 5 mL on days 30 and 60. For blood sampling, fish were anaesthetized with MS222 (Sigma Aldrich, Steinheim, Germany) [
Red blood cells (RBC, 106 mm3), hematocrit (Hct, %) and hemoglobin (Hb, g/dL) were determined by using the method by Blaxhall and Daisley [
and
Total myeloperoxidase (MPO) content was measured according to Quade and Roth [
Serum lysozyme was assessed using the turbidometric assay [
Biochemical indices in serum including glucose (GLU), total protein (TPROT), albumin (ALB), triglyceride (TRI), cholesterol (CHOL) globulin (GLO) were determined using bioanalytic test kits (Bioanalytic Diagnostic Industry, Co) and measured by a spectrophotometer (PG Instruments, UK). Serum globulin was determined by the following formula; globulin = total protein − albumin.
In this study, the variation analyses were carried out with Duncan multiple comparison tests, and the differences between groups were carried out via the use of SPSS 17 statistics program in order to evaluate the relationships between the data of blood, proximate composition and growth parameters obtained from the test group.
Growth results are presented in
Control | C1 | C3 | C5 | |
---|---|---|---|---|
IW (g) | 11.32 ± 0.27a | 11.07 ± 0.54a | 10.67 ± 0.16a | 10.75 ± 0.29a |
FW (g) | 27.40 ± 0.57a | 26.49 ± 0.21a | 26.71 ± 0.67a | 28.27 ± 0.35a |
WG (g) | 16.09 ± 0.78a | 15.41 ± 0.64a | 16.04 ± 0.63a | 17.52 ± 0.49a |
FCR | 0.97 ± 0.05a | 1.01 ± 0.13a | 1.06 ± 0.05a | 0.95 ± 0.05a |
SGR (%/d) | 1.47 ± 0.07a | 1.45 ± 0.09a | 1.53 ± 0.04a | 1.61 ± 0.05a |
Values are mean ± SE (n = 6). Within a row, means with differing letters are significantly different (P < 0.05).
The whole-body proximate compositions of fish at the end of the experiment are presented in
It is often suggested that hematological parameters are useful stress or disease indicators for fish; and the changes in RBC count, Hct value, Hb value and erythrocyte indexes are important to detect organ health status [
Myeloperoxidase is contained in the polymorphonuclear neutrophils, monocytes, and macrophages [
In the present study and other similar studies showed that non-specific immune responses exhibited significant enhancement in their activity in different time of feeding with the carvacrol diet and didn’t show any modulation of the immune parameters on all sampling days. It is known that the fish innate immune system lacks memory, the duration of its response is always shorter than the specific system [
Serum glucose has often been suggested as a useful nonspecific stress indicator [
The increase of serum protein, albumin and globulin levels indicates the increase in innate immune response of fish [
Composition (%) | Control | C1 | C3 | C5 |
---|---|---|---|---|
Protein | 17.81 ± 0.58a | 18.02 ± 0.47a | 16.51 ± 0.58a | 16.78 ± 0.62a |
Lipid | 6.28 ± 0.80a | 5.56 ± 0.29a | 6.66 ± 0.61a | 6.07 ± 0.18a |
Ash | 2.72 ± 0.10a | 2.58 ± 0.08a | 2.60 ± 0.02a | 2.51 ± 0.04a |
Moisture | 72.94 ± 1.30a | 73.10 ± 0.03a | 73.22 ± 0.41a | 73.22 ± 0.15a |
Values are mean ± SE (n = 6). Within a row, means with differing letters are significantly different (P <0.05). (See
Blood Parameter | Control | C1 | C3 | C5 |
---|---|---|---|---|
Hb (g∙dL−1) | 5.07 ± 0.15a | 5.26 ± 0.18a | 4.87 ± 0.16a | 5.00 ± 0.37a |
Hct (%) | 35.60 ± 0.42a | 37.80 ± 0.30a | 37.00 ± 0.58a | 36.60 ± 0.67a |
RBC (106mm3) | 3.55 ± 0.06a | 3.78 ± 0.06a | 3.70 ± 0.07a | 3.65 ± 0.09a |
MCV (fL) | 100.42 ± 0.43a | 100.14 ± 0.56a | 100.03 ± 0.49a | 100.21 ± 1.00a |
MCH (pg) | 14.31 ± 0.50 a | 13.93 ± 0.44a | 13.19 ± 0.49a | 13.66 ± 0.96a |
MCHC (g∙dL−1) | 14.25 ± 0.48 a | 13.92 ± 0.45a | 13.18 ± 0.46a | 13.67 ± 1.02a |
Hb, haemoglobin; Hct, hematocrit; RBC, red blood cells; MCV, mean cell volume; MCH, mean cell haemoglobin; MCHC, mean cell haemoglobin concentration. Data represent as mean ± SE. Within a row, means with differing letters are significantly different (P < 0.05). (See
Days | Control | C1 | C3 | C5 | |
---|---|---|---|---|---|
GLU (mg/dL) | 30 | 119.26 ± 5.28a | 141.12 ± 8.67a | 139.42 ± 17.52a | 136.93 ± 11.06a |
60 | 116.83 ± 6.63a | 63.18 ± 4.16b | 59.90 ± 5.28b | 54.88 ± 8.63b | |
TPROT (g/dL) | 30 | 8.72 ± 0.87a | 10.63 ± 1.07a | 10.21 ± 0.39a | 10.02 ± 0.87a |
60 | 7.89 ± 0.34bc | 9.27 ± 0.52b | 11.25 ± 0.61a | 7.40 ± 0.53c | |
ALB (g/dL) | 30 | 3.06 ± 0.31a | 2.93 ± 0.29a | 3.07 ± 0.34a | 3.58 ± 0.54a |
60 | 2.43 ± 0.06a | 2.57 ± 0.11a | 2.22 ± 0.04a | 2.39 ± 0.16a | |
GLO (g/dL) | 30 | 5.65 ± 0.91a | 7.71 ± 1.01a | 7.14 ± 0.38a | 6.44 ± 0.87a |
60 | 5.47 ± 0.36bc | 6.70 ± 0.47b | 9.03 ± 0.59a | 5.01 ± 0.56c | |
TRI (mg/dL) | 30 | 124.11 ± 12.64a | 130.85 ± 12.29a | 121.81 ± 13.40a | 112.32 ± 17.01a |
60 | 161.91 ± 12.76b | 151.28 ± 12.21b | 215.96 ± 17.76a | 154.89 ± 8.35b | |
CHOL (mg/dL) | 30 | 253.07 ± 12.31a | 260.33 ± 10.21a | 253.33 ± 11.02a | 153.53 ± 15.76b |
60 | 178.08 ± 12.16a | 187.20 ± 8.84a | 178.56 ± 9.23a | 192.24 ± 10.23a |
Values are mean ± SE (n = 6). Within a row, means with differing letters are significantly different (P < 0.05). (See
comparison with the control, C1 and C5 treated groups. In addition, serum ALB levels were similar in all treatment groups.
Major blood lipid components, such as triglycerides, phospholipids, and cholesterol are affected by diet and stress levels in fish [
In conclusion, the results of the present study indicate that dietary supplementation of 3 g/kg of carvacrol in commercial diets could improve some non-specific immune and biochemical status in rainbow trout, without adversely affecting hematological parameters, growth performance or feed utilization. Thus, carvacrol can be utilized as health promoter in fish culture. Further investigation on the potential effects of carvacrol on control of trout diseases is encouraged.
We would like to thank the Çanakkale Onsekiz Mart University Research Fund for financial assistance (the project number COMU BAP FDK-2013-102) and Adnan ÇOBAN for providing research facilities.