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In the last years, there were some bacterial outbreaks occurred during the summer season of farm-raised Oreochromis niloticus at Kafr El-Sheikh and Dakahlia Governorates resulting in high fish mortalities and severe economic losses in these farms. So, this study aimed to detect the causes of the summer fish mortalities in these governorates to facilitate the diagnosis methods of study pathogens. Thirty fish farms were surveyed (20 in Kafr El-Sheikh and 10 in Dakahlia). 150 examined diseased fish (five from each farm) were succumbed for bacteriological isolation and biochemical and molecular identification. LD 50 experiments were done to detect the infectivity and pathogenicity of some strains of bacterial isolates. The obtained results cleared that O. niloticus summer mortalities were caused by mixed infections with different bacterial species. The isolated bacterial species were 9 types of bacteria; 7 gram negative bacteria; 78 (30.5%) Aeromonas hydrophila, 52 (20.3%) Pseudomonas aeruginosa, 40 (15.6%) Vibrio anguillarum, 20 (7.8%) Edwardsiella tarda, 12 (4.7%) Edwardsiella ictulari, 10 (3.9%) Pseudomonas fluorescens, 7 (2.7%) Flavobacterium columnare and 2 gram positive bacteria; 30 (11.7%) Streptococcus agalactia and 7 (2.8) Enterococcus feacalis which were the most prevalent bacteria affecting fish farms and implicated in the O. niloticus seasonal summer mortalities and LD 50 experiments confirmed the pathogenicity of some isolated bacteria. From the obtained results, it could be concluded that, the main cause of summer fish mortalities in studied farms was 81.82% gram negative bacteria and 18.18% was gram positive bacteria.

Key words:Aeromonas hydrophila, Fingerlings, Oreochromis niloticus, Refeeding, Starvation Knowledge of how fish respond to starvation periods could provide a basis for improved nutrition, rearing, disease control and thereby help to optimize Oreochromis niloticus culture. In the current study, the effect of alternative starvation-refeeding regime was monitored on some growth, hematological and serum biochemical parameters in Nile tilapia fingerlings; followed by checking the role of these feeding schedules in combating the disease challenge. The study was performed in glass aquariums at the aquaculture research unit, Sakha, Kafr El-Sheikh governorate, Egypt using 375 Oreochromis niloticus fingerlings weighing 29±0.5 gram. Fingerlings were subjected to different starvation periods (7, 10, 14, 21 days), followed by 30 days of refeeding on a commercial fish ration (25% protein). Fish growth parameters, hematological and serum biochemical parameters were recorded before starvation, before refeeding and after 30 days of refeeding. The experimental challenge was carried out to determine the effect of different starvation intervals followed by refeeding regimes on the immunity of O. niloticus fingerlings; against bacterial infection with Aeromonas hydrophila through recording mortality rates and the histopathological finding.The collected results revealed that fingerlings can recover all the hematological and serum biochemical parameter values of all food deprived groups close to the normal level of full-fed control fish; concluding that O. niloticus can easily be cultured on suitable economic short-time feeding regime with subsequent refeeding in alternate days without any significant differences in fish size and final production (reducing the food amount and cost required for production cycle). Besides, short-term starvation prior to a bacterial infection followed by subsequent refeeding could promote the defense mechanism of the fish to fight against Aeromonas hydrophila.

Ten Arabian foals aged 3-8 months, at private farm in Sharkia Province were used in this study, which continued from 1 st of December 2003 till the end of June 2004. The foals were divided into two equal groups of five foals each. The animals in the first group were weaned at 3 months of age while, those in the second group were weaned normally at 5 months of age. The first group foals spent less time in eating (43.32±5.22 vs 45.52±6.22% of their time), in standing rest and lying than the second group foals, but spent more time in standing alert (4.55±1.32 vs 4.12±1.53% of their time). The foals of first group had a lower body weight gain during the period of study than that normally weaned foals. The foals which weaned early at 3 months had engaged in stereotypies behaviour such as steps, head threat, bite threat, bite, kick threat and kick more than that foals which were weaned normally at 5 months, there was a significant difference in the level of cortisol hormone post-weaning between early weaned foals and normally weaned foals. In conclusion weaning of foals at 5 months of age was less stressful, more comfort and achieve good welfare for foals than early weaning.

Poultry producers accustomed to use light colours in broiler production as atrial to increase their productivity, especially in the developing countries to cover the animal protein gap. This experiment was planned to study the effect of different blue light colour intensities (high, medium and dim) on a recently imported Indian River (IR) broilers to Egypt. In this study, 270 one-day old Indian River broiler chicks were used. The birds were exposed to high blue light intensity (HBLI), medium blue light intensity (MBLI) and dim blue light intensity (DBLI), through a monochromatic lighting system that was installed in different rooms for 24 hours daily. The birds were randomly divided and housed into three well controlled pens of 5.46 m2 with three replicates of 30 each using a density of 17 birds/m2 in the room. The results showed that the broilers reared under DBLI had a significantly (p< 0.05) higher body weight, body weight gain, Newcastle disease virus antibody titer and foot pad dermatitis with obviously, economic Feed conversion ratio (FCR) and low activities and heterophyil/lymphocyte ratio in comparing with (MBLI) and (HBLI). In conclusion, poultry producer can use dim blue light in their farms to reduce the activities and increase the productivity of the birds.

This work was carried out on a number of 800 broiler breeder fertile eggs from a commercial broiler strain (Lohmann) which reared on a deep litter system at Menoufia Governorate, Egypt. This experiment was begun in September 1, 2003. All selectable eggs were divided into 20 groups (40 each). The first nine groups were stored for different periods (0, 3, 6, 9, 12, 15, 18, 21 and 24 days). The groups from 10 to 13 were stored for 6 days and differ only in the number of egg turning during the storage (0, 3, 6 and 12 times / day) period. The groups 14, 15 and 16 were selected on the basis of egg weight (35 to 45, 46 to 55 and 56 to 65g). While, the groups from 17 to 20 were selected from different flock ages 34, 44, 54 and 64 weeks. This work was conducted to study the effect of flock age, egg weight, duration of egg storage and number of egg turning during pre-incubation storage on fertility, hatchability, incubation period, post-hatching chick weight and chick weight at 7 days old in addition, egg weight loss during different storage periods. Egg weight loss increased with each three days increasing in the storage period. The incubation period, posthatching weight and chick weight after 7 days old were increased by increasing the flock age and egg weight while, the fertility percent and hatchability of fertile eggs were decreased. Also, the fertility percent, hatchability of fertile eggs, post-hatching weight and chick weight after 7 days old were decreased by increasing the duration of storage but, the incubation period was increased. Increasing the number of eggs

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