الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
 |  | from | 178 |  |  |
| | | from | 178 | | |
Abstract
The present work was done during the production season 2012 from May to August using the facilities provided by department of Animal Husbandry and Animal Wealth Development, Faculty of Veterinary Medicine, Alexandria University. African catfish were our experimental fish. Two experiments were practiced: The first: Studying the effect of hormones alone or in combination with the dopamine antagonist domperidone (Dom) depending on eggs and larvae qualities. The second: Studying the effect of feed types and stocking densities on growth performance, survivability and cannibalistic activity of African catfish larvae.
During the experimental period all females African catfish were injected in the dorsal muscle by one of different combination. Saline 1 ml kg-1 BWT, Dom 10 mg kg-1 BWT, CPE 4 mg kg-1 BWT, CPE plus Dom 4 +10 mg kg-1 BWT, HCG 4000 IU, HCG plus Dom 4000 IU + 10 mg kg-1 BWT, LHRHa 50 μg, LHRHa plus Dom 50 μg + 10 mg kg-1 BWT, GnRHa 40 μg and GnRHa plus Dom 40 μg + 10 mg kg-1 BWT for T1, T2, T3, T4, T5, T6, T7, T8, T9 and T10 respectively.
Results indicated successful spawning induction using different spawning agents; carp pituitary extract (CPE), human chorionic gonadotropin (HCG), luteinizing hormone releasing hormone analogues (LHRHa) and GnRHa with or without dopamine antagonist (Dom). Females treated with different hormones combined with the dopamine antagonist (Dom) successfully ovulated with a 100% ovulation rate. On the other hand, the use of LHRH-a or GnRHa alone resulted in low percentage of ovulated females as presented by low ovulation rate (12.5), (25%) in T7 (LHRHa treated fish) and T9 (GnRHa treated fish) respectively.
The ovulation index, latency period and weight loss after ovulation were in the range of 12.64 to 70.76 %, 11.75 to 21 hrs and 1.10 % to 9.83 %; respectively. where the lowest ovulation index (12.64 %), the highest latency period (21 hrs) and the lowest weight loss after ovulation (1.1%) observed in T7 (LHRHa treated fish). The highest ovulation index (70.76 %) and a better trend of synchrony in ovulation and the highest weight loss after ovulation (9.83%) was achieved in T10 (GnRHa plus Dom treated fish). Additionally, T7 (LHRHa treated fish) had the lowest weight of egg produced per female (3.12 g) While, the highest value was (40.82 g) was attained by T8 (LHRHa plus Dom treated fish).
Concerning the fertilization rate, T9 (GnRHa treated fish) had the lowest percentage of fertilization (74.16 %), (51.16 %) not only after 12 hrs but also after 24 hrs of incubation. whereas, the highest fertilization rate (91.29 %), (85.29 %) were observed in T10 (GnRHa plus Dom treated fish) both after 12 hrs and 24 hrs of incubation respectively. A similar trend of low hatchability percentage (75.16 %), survival rate (55.83 %), and number of live larvae 2 days after hatch (3607 larvae) were observed in T9 (GnRHa treated fish), whereas, T10 (GnRHa plus Dom treated fish) had the highest survival rate (89.91%) and live larvae two days after hatch (15864 larvae), together with the lowest percentage (2.12 %) of deformed larvae.
With the exception of T9 (GnRHa treated fish) the hatchability percentage was comparable among the other treatments but still the highest number of the hatched eggs (19078 hatched eggs) and the highest percentage of deformed larvae (10.50 %) were recorded for the broodfish females in T6 (HCG plus Dom treated fish) and T8 (LHRHa plus Dom treated fish).
Comparing the effect of different feed types and stocking densities on growth, survival and cannibalism of the catfish larvae nine treatments were conducted. T1 received Artemia nauplii and 10 larvae l-1, T2 received Artemia nauplii and 20 larvae l-1, T3 received Artemia nauplii and 40 larvae l-1, T4 received Zooplankton and 10 larvae l-1, T5 received Zooplankton and 20 larvae l-1, T6 received Zooplankton and 40 larvae l-, T7 received Dry feed and 10 larvae l-1, T8 received Dry feed and 20 larvae l- and T9 Dry feed and 40 larvae l-1.
T1 (Artemia nauplii and 10 larvae l-1), T9 (Dry feed and 40 larvae l-1) had the highest growth performance parameters and a significantly lower growth performance parameters respectively as expressed by final body weight (T1; 165.03 mg, T9; 34.36 mg), average daily gain (T1; 8.16 mg day -1, T9; 1.63 mg day -1) and specific growth rate ( T1; 22.83% day-1, T9; 14.83% day-1) by the end of the rearing experiment. Meanwhile, the mortality rate percentage and survival rate percentage was the lowest (10.51%) and the highest (82.37 %); respectively in T4 (Zooplankton and 10 larvae l-1) where, T9 (Dry feed and 40 larvae l-1) had the highest (42.86 %) and the lowest (29.37%) values; respectively.
Additionally, higher stocking densities of catfish larvae had expressed higher rates of cannibalism when compared to the lower stocking densities where the lowest cannibalism rate (3.46%) recorded for T1 (Artemia nauplii and 10 larvae l-1) by the end of the experiment.
On the basis of these results it would be concluded that:
Induced spawning of the African catfish was successfully carried out using different spawning agents with or without dopamine antagonists domperidone. However, from all the reproductive parameters investigated, GnRHa combined with dopamine antagonists domperidone injected gravid C. gariepinus had higher number of spawned and fertilized eggs, hatchlings, a better trend of synchrony in ovulation, the highest weight loss after ovulation, low number of deformed larvae and high survival rate. Thus much beneficial over the other spawning agents used in the present study either with or without the dopamine antagonists (Dom) for induced breeding of African catfish and its use is recommended. But still further studies are required to investigate the effect of using different doses of such spawning agents combined with or without different dopamine antagonists and their economic efficiency in spawning induction of African catfish C. gariepinus.
Concerning the rearing experiment, it was clearly indicated that catfish larvae were successfully reared and performed well from the stand point of growth performance, survival rate and cannibalism rate at lower stocking density 10 larvae l-1 when fed on either Artemia or zooplankton. However, further investigations are required to explore the effect of using other dry feed types during the rearing phase of African catfish larvae.