This study was conducted to develop a short-term immersion procedure for masculinisation of Nile Tilapia (Oreochromis niloticus) by using 17α-methyltestosterone at 100, 200 or 400 µg l-1 for 3, 6 or 12 h. Fry were immersed two successive times with 3 days interval period. The highest percentage of male Oreochromis niloticus (96±4 %) and the lowest gonado-somatic index of female Oreochromis niloticus (1.89±0.02) were obtained by immersion of fry in 17α-methyltestosterone at the level of 400 µg l -1 for 6 h. However, survival rate of Oreochromis niloticus Fry during hormone treatment period did not differ significantly from survival rate in the control group. Tilapia culture is widespread all over the world. The problem of overpopulation in fish ponds caused by uncontrolled reproduction is a major constraint to the further development of the Tilapia culture industry. This problem could be overcamed by culturing all-male populations of Tilapia. One of the most common techniques for producing all-male populations of Tilapia is androgen-induced-sex-reversal by using androgen-treated feed. However, the immersion of fry is not fully developed for practical usage. Feeding androgen carries some potential disadvantages as in efficiency in masculinisation. Immersion of Tilapia fry in androgen solutions may be an alternative to oral administration of androgen, this technique is well developed in salmonid culture; however it remains largely experimental in Tilapia culture. The objective of this research was to develop short-term immersion procedure for the masculinisation of Nile Tilapia by using 17α-methyltestosterone and evaluating the most proper dose concentration and hormone treatment period.
ABDUSSALAM ABUMHARA(10-2009)

This study was conducted to investigate the prevalence of Newcastle Disease, Avian Influenza, Infectious Bronchitis, and Infectious laryngotracheitis in some regions of Tripoli-Libya. Serum samples were collected from Four broiler farms in Wadi Alrabea area, two layer farms and one backyard farm in Gaser Bin Gasher, two layer farms in Alswani and one backyard farm in Zliten City and screened for the presence of antibodies against LPAI-H9, HPIA-H5, HPIA-H7, ND, IB 4/91 strain using the HI test and antibodies against ILT virus by ELISA. The overall seroprevalence of H9, H5, H7, ND, IB4/91 and ILT was 26.5%,0%,0%,, 29.5%,43% and 30% respectively. All sera tested for AI-H5 and AI-H7 were negative. In Wadi Alrabea flocks, seroprevalence of H9, H5, H7, ND, IB4/91 and ILT was 44%, 0%, 0%, 16.28%, 32.56% and 0% respectively. Where as in Gaser Bin Ghasher, was 24%,0%, 0%, 33.87, 36.29% and 39% respectively. In Alswani, the seroprevalence was 8.70%, 0%, 0%, 52.17%, 54.35% and 54.3%. The seroprevalence of H9, H5, H7 in Gaser Bin Ghasher backyard chickens was 23%, 0%, 0% respectively and the seroprevalence of H9, H5, H7, ND, IB4/91 of Zliten backyards was 12%, 0%, 0%, 12%, 96% respectively. Further investigations are recommended to identify the circulating virus genotypes and models of transmission for better understanding of these viruses epidemiology in backyard chickens in Libya. Vaccination of backyard chickens against ND using heat resistant strain is highly recommended.
Housen Ashareef Mohammed, Abdulatif Abdulaziz Asheg (10-2021)

ِAbdulatif Asheg, Khalid Fathi Almasri (1-2020)