الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
 |  | from | 104 |  |  |
| | | from | 104 | | |
Abstract
SUMMARY AND CONCLUSION
This study was conducted at the Aquaculture Laboratories of the Animal Production Department, Fish production Branch at the Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Cairo, Egypt.
This study consisted of 10 treatments to evaluate the physiological and reproductive performance, growth performance and blood biochemistry indices. In addition to inspection of gills, liver, kidneys, and gonads histological sections of monosex tilapia fingerlings that were fed contaminated experimental diets with different concentrations of AFB1 for a period of 113 days. Also, compared them with monosex tilapia fingerlings that were exposed to two mitigation procedures either stopping the feeding on the contaminated diets or adding Vit. C supplementation combined with AFB1 to study the extent of recovery process of the experimental fish. As well as, following up growth performance and body chemical composition changes, blood count, liver, and kidney activity enzymes in addition to the gonadal changes through the course of the experiment. In this study, the fish were fed on diets containing 30% protein, with different levels of aflatoxin. The fish were fed at a rate of 5% of the live mass.
The study included three categories divided as follows:
Category (1):
(T1) 20 µg AFB1 kg-1 of diet throughout the study period.
(T4) 40 µg AFB1 kg-1 of diet throughout the study period.
(T7) 80 µg AFB1 kg-1 of diet throughout the study period.
Category (2):
(T2) 20 µg AFB1 kg-1 of diet from the beginning of the study until 57 days, then changing the feed to uncontaminated feed.
(T5) 40 µg AFB1 kg-1 of diet from the beginning of the study until 57 days, then changing the feed to uncontaminated feed.
(T8) 80 µg AFB1 kg-1 of diet from the beginning of the study until 57 days, then changing the feed to uncontaminated feed.
Category (3):
(T3) 20 µg AFB1 kg-1 of diet throughout the study period, with the addition of vitamin C from the day 58 of the study period until the end.
(T6) 40 µg AFB1 kg-1 of diet throughout the study period, with the addition of vitamin C from the day 58 of the study period until the end.
(T9) 80 µg AFB1 kg-1 of diet throughout the study period, with the addition of vitamin C from the day 58 of the study period until the end.
All categories were compared to control treatment (T0) fed uncontaminated diet.
The results are summarized in the following:
1. Growth performance and survival rate
By comparing the three categories together, we can conclude that the results of the second category were very similar to the third category, where T2 in the second category scored the highest values of TWG and ADG were 24 g and 0.18 g fish-1 day-1, respectively. Also, the highest TWG was 23.3 g, ADG was 0.17 g fish-1 day-1 achieved in T9 of the third category. Meanwhile the first category scored the lowest values in growth performance as TWG (21 g) and ADG (0.16 g fish-1 day-1) in T7. While survival rate was decreasing in parallel with increasing the applied concentration of AFB1. It’s observed that when fish fed on diet with the higher aflatoxin concentration (T7) reduced SR by 7.9%, compared to fish fed T0 that recorded the highest SR% compared to the other experimental groups.
2. Chemical composition of the whole fish body
In general, there were no significant effects (P < 0.05) on the chemical composition of the experimental fish in CP %, lipid %, and ash % between the three categories.
3. Hematology
As a general scope, the results of the second category were remarkably close to the results of the third category, and the first category recorded the worst blood indices.
The biochemical parameters indicated that, T7 diet (first category) had scored the lowest RBCs, Hb, and Hct by 30.7, 12.1 and 23.9 %, respectively but increased WBCs by 43.7 % compared with fish fed T0 diet. In the second category the results showed that fish fed T8 (80 µg AFB1 kg-1 diet) had reduced Hb by 8.2 % and increased RBCs, WBCs and Hct by 8.2, 44.3 and 14.9%, respectively compared to fish fed T0 diet. In the third category T9 (80 µg AFB1 kg-1 diet + vit. C) had reduced Hb by 6.6 % and increased RBCs, WBCs and Hct by 36.4, 27.0 and 41.9%, respectively compared to fish fed T0 diet. In all categories, it could be noticed that high concentration of AFB1 (80 µg kg-1) clearly increased WBCs compared with other treatments indicating that fish were more stressed.
4. Liver and kidney functions
The biochemical parameters of liver and kidney enzymes were increasing in parallel with increasing the applied concentration of AFB1. In the first category that fish fed with a higher aflatoxin diet T7 (80 µg AFB1 kg-1 diet) recorded the highest values of ALT (13 IU/L), and creatinine (0.23 mg/dl). In the second and third categories there was some improvement in both ALT and creatinine values due to shifting to uncontaminated diet or adding vitamin C.
5. Hepatosomatic index
Hepatosomatic index was significantly affected (P<0.05) by all treatments. In the first category, a higher aflatoxin diet T7 (80 µg AFB1 kg-1 diet) scored 2.11 % higher values of HSI compared to (1.52%) for the highest concentration of aflatoxin in the second category and (1.7%) in the third category compared to fish fed T0 diet.
6. Histological examination
6.1 Liver
Aflatoxin can cause such degeneration and necrosis in liver tissue. The results of histological examination of the liver in the control group showed a normal structure. Whereas histopathological alternations were observed in the liver tissues of fish exposed to higher concentrations of AFB1 for 113 days. While, in the second category shifting from aflatoxin contaminated diet to non-contaminated diet showed an improvement sign in liver structure. A similar improvement in liver structures was also observed in the third category as diet was supplemented by 100 mg kg-1 vitamin C. The supplementation of vitamin C has mitigated the damage caused by aflatoxin B1.
6.2 Kidney
Vacuolization, degeneration, necrosis, and inflammatory infiltration in kidney tissue are signs of aflatoxin exposure. The results of the control group showed a normal kidney structure. While the deterioration in kidney structure has been shown in the first category that was exposed to AFB1 with an ascending concentration for 113 days. While in the second category, fish that shifted from an aflatoxin-contaminated diet to non-contaminated diet showed signs of improvement in kidney structure. A similar improvement in kidney structures was also observed in the third category where diet was supplemented with 100 mg kg-1 vitamin C.
6.3 Gills
Histological disorders such as atrophy, curling, oedema, hyperplasia and/or hypertrophy and fusion of epithelial cell are signs that can be caused by AFB1 were investigated in the gills tissue sections of O. niloticus fingerlings. Some of these signs were observed in gill tissue sections of fish exposed to different concentration of AFB1 for 113 days exposure periods. However, there was some improvement in these signs after switching to non-contaminated diets (second category) or by adding vitamin C in the third category.
6.4 Testes
Our findings illustrated that testicular sections from fish fed zero AFB1 (T0) displayed normal structure with spermatozoa filling the testis lumina compared to the other treated fish groups. Testicular deterioration was observed in all AFB1 treated group, which was pronounced in fish exposed to high level for 113 days experimental period (first category) compared to other treated fish categories. Neither shifting to non-contaminated diet nor supplementation of vitamin C completely recover testicular structure as indicated by disorder of testicular architecture, degeneration of germ-somatic cells and the presence of few cysts of spermatozoa.
CONCLUSION
The present data showed that feed contaminated with AFB1 (Aspergillus flavus) at concentrations up to 80 µg AFB1 kg-1 of feed showed significant negative differences compared with the uncontaminated feed. Those differences in terms of the productive performance of fish are represented in growth performance (TWG, ADG and SGR), feed efficiency parameters (FCR, PER and PPV) and survival rate. Furthermore, the hematological and serum biochemistry parameters (ALT, AST, and creatinine), and HSI. However, the kidney, liver, gills, and testes tissues suffered damage from AFB1 contaminated diets. Thus, the available evidence suggests that vitamin C supplementation can have a beneficial effect on both fish health and productivity in the presence of AFB1. However, it is important to note that the optimal dosage and duration of vitamin C supplementation may vary depending on the specific conditions of the culture system and the degree of aflatoxin contamination.
The damage caused by feeding with feed contaminated with different concentrations of aflatoxin continued the testicular tissue and did not improve after stopping feeding with the contaminated feed (2nd category) or by adding vitamin C (3rd category). from the results of this study, it can be said that low levels of aflatoxin, which may result from poor feed storage, negatively affect the growth rates of fish. However, they can be used to feed fish after adding vitamin C to reduce their harmful effects. It is worth noting that the results of the study indicate avoiding the use of contaminated feed in feeding broadstock because of its obvious harm to fish fertility.
Finally, further attempts are seriously required regarding determining the suitable level of vitamin C, and the optimum recovery period as protective strategies against aflatoxicosis not only for O. niloticus but also for other fish species.