A two level factorial experiment (3 × 3) was designed to evaluate the effect of dietary inclusion level of probiotic and breed on productive performance, immune status and egg quality characteristics in laying hens reared under high ambient temperature. A total of 216, 32-week-old laying hens representing three different breeds (White Leghorn, Saudi black and Saudi brown) were randomly assigned to three dietary treatments (0, 200 and 400 g/t feed) in a 90-d experiment. The current results indicated that the inclusion of probiotics in layer diets did not appear to cause any adverse effects on egg production traits compared with non-treated hens. Dietary supplementation with probiotics at 400 ppm level significantly (p < .05) increased shell thickness compared to non-treated laying hens. Moreover, an improvement in eggshell quality and breaking strength in hens fed a diet containing probiotics was observed under high ambient temperature. Also, plasma cholesterol and triglyceride were reduced in laying hens fed a diet supplemented with probiotics. Furthermore, probiotic inclusion significantly increased IgM immunoglobulin concentration in laying hens fed a diet containing either 200 or 400 ppm compared with untreated hens. Concerning breed effect, Saudi black laying hens recorded significantly (p < .02) higher egg mass compared with the other breeds. Also, both Saudi chicken breeds exhibited significantly higher cell-mediated response and IgM concentration compared with Leghorn hens.

1. The objective of the study was to evaluate the potential effects of dietary probiotic supplementation and stocking density and their interaction on growth performance, humoral and cellular immune responses of broiler chickens raised under hot climate conditions. 2. A total of 1800 1-d-old unsexed broiler chicks (Ross 308) were allocated in a completely randomised 3 × 2 factorial design, with three concentrations of dietary probiotic (0, 200 and 400 mg/kg) containing 4 × 10⁹ cfu/g of Bacillus subtilis and two stocking densities (12 or 18 birds/m²) in a total of 6 treatment subgroups. 3. Dietary probiotic and stocking density had no significant effect on live body weight, feed consumption and feed conversion ratio. 4. Dietary probiotic supplementation had a positive effect on serum immunoglobulin M (IgM) and cell-mediated immunity when compared to the control at 6 weeks of age, whereas serum immunoglobulin A (IgA) and immunoglobulin Y (IgY) were improved, but not significantly so. Dietary probiotic and stocking density had no effect on relative weights of the bursa of Fabricius and spleen. 5. Dietary probiotic supplementation had a positive significant effect on serum IgM concentration and cell-mediated immunity without penalising growth performance in broilers raised under high ambient temperature.

High ambient temperatures in tropical and subtropical regions adversely affect the growth and egg productive performance of both broiler and laying chickens. Relative humidity and ventilation rate influences bird's performance, particularly when they are reared in open sided poultry houses. Genetic approaches that aid in reducing or altering the extent of plumage cover has, as a result, been adopted in many hot regions. Fortunately, there are some major and marker genes can reduce the deleterious effects of heat stress, naked neck (Na) and frizzle (F) genes being the most notable ones. The bulk of relevant literature has shown that their favourable effects on growth and laying performance are well established. Therefore, the naked neck and frizzle genes can be a viable alternative for broiler and layer production particularly, in the tropical countries where summer temperatures are very high.

1. A study was conducted to evaluate the relationship among physical and mechanical properties of the eggshell, as affected by breed and hen’s age. 2. Data on eggshell quality (external characteristics and derived measurements) were obtained from 322 laying hens, from three breeds (Fayoumi, Dandarawi and Hy-Line Brown) during the laying cycle, starting from 38 wks of age for four experimental periods (38, 46, 54 and 62 wks). 3. Eggs obtained from the Fayoumi breed exhibited the highest shell thickness and breaking force. There was a linear improvement in eggshell quality attributes associated with hen’s age up to 54 wks, thereafter a deterioration was found for all breeds. 4. Generally, eggs laid by native breeds (Fayoumi and Dandarawi) had better mechanical properties compared to those produced by the commercial strain (Hy-Line Brown). In addition, the interaction between breed and hen’s age was not significant for all physical properties and mechanical attributes. There was a highly significant (P≤0.01) positive correlation between the breaking force and either eggshell toughness or shell thickness, and regression analyses suggested that eggshell toughness was the best predictor for breaking force, followed by shell thickness.

The influence of subcutaneous injections of silver nanoparticles (AgNPs) on rabbit performance, hematological and biochemical parameters of blood, antioxidant status, and the residues of silver in meat and blood in two breeds (New Zealand White (NZW) and Jabali) of rabbits growing under high ambient temperature was evaluated. A total of 90 six-week-old rabbits (45 NZW and 45 Jabali) were randomly distributed into three equal treatment groups (control, 0.5 mg, and 1.0 mg AgNPs/kg body weight). The treated rabbits were injected twice a week for four consecutive weeks. The results revealed that AgNPs administration had no significant effect on average daily gain (ADG), feed intake, and feed conversion ratio (FCR). The NZW breed surpassed the Jabali breed in growth performance traits, carcass weight, dressing percentage, and cuts of mid parts and hind cuts. Administration of AgNPs had a significant effect on hematocrit (HCT) and platelet (PLT) values. Rabbits injected with AgNPs at a dose of 0.5 mg showed a lower plasma concentration of total cholesterol and triglycerides than that of control rabbits. The NZW breed had significantly low platelet, total cholesterol, and triglyceride values. Rabbits injected with 0.5 mg/kg BW had the lowest total antioxidant capacity and highest malondialdehyde (MDA) and glutathione peroxidase. The Ag residues were higher in blood than those in meat in treated rabbits. The local breed (Jabali) had significantly lower residues than the imported one (NZW) either in meat or in blood. However, the amount of accumulated silver in blood plasma and meat increased with increasing dose.