Effect of genotype of growing rabbits on the productive performance with special reference to residual feed intake at hot temperature

Objective

Better feed efficiency can be achieved by selecting rabbit genotypes with lower residual feed intake (RFI) under high ambient temperatures.

Methods

Two genotypes of rabbits (Jabali, Saudi local breed and imported, Spanish V-line) were used to derive RFI and to investigate the relationship between RFI and productive traits. In total, 250 animals (125 each) were housed in individual wire mesh cages in a semi-closed rabbitry. Growth performance, feed criteria, carcass evaluation, biochemical blood analysis, and immune responses were determined.

Results

Superiority in growth performance, feed efficiency, carcass characteristics, and cellular immunity was recorded in the Jabali breed compared to the V-line genotype. According to regression analysis, a significant effect of daily body weight gain was found, upon computing the expected feed intake in both genotypes. Moreover, mid-body weight0.75 had a significant effect only in the Jabali breed. Positive correlation coefficients between RFI and dry matter feed intake or feed conversion ratio were found. The same trend in this relationship between RFI and productive traits was observed in some cases for both genotypes. An opposite trend in correlations was observed in the studied genotypes for some traits.

Conclusion

The results suggest that the relationship between RFI and productive traits must be taken into consideration in rabbit breeding programs under the prevailing environment. However, further studies are required to investigate the effect of rabbit genotype and environmental factors on computing RFI.

Effect of propolis supplementation and breed on growth performance, immunity, blood parameters and cecal microbiota in growing rabbits

Objective: The present study was conducted to investigate the potential effects of dietary supplemented propolis in two growing rabbit breeds on growth performance, immune response, blood parameters, carcass characteristics, and cecal microflora composition.Methods: A total of 90 growing rabbits aged 6 weeks from two breeds (V-line and Jabali) were randomly allocated to 3 dietary propolis experimental treatments. The experimental treatments consisted of a 2×3 factorial arrangement with two rabbit breeds and three levels of dietary propolis supplementation (0, 250 mg/kg, and 500 mg/kg). Each sub-treatment has 15 rabbits. The experimental period lasted six weeks.Results: There were no significant differences in growth performance and carcass characteristics due to propolis administration. Propolis supplementation at a high level significantly increased (linear; p<0.05) cellular-mediated immunity compared with the unsupplemented group. Furthermore, the rabbits receiving propolis exhibited a significant increase (linear and quadratic; p<0.03) in IgM immunoglobulins compared to the control. The current study provides further evidence that the dietary inclusion of propolis can significantly reduce pathogenic bacterial colonization in growing rabbits. The total count of microflora, E. coli, and Salmonella spp. was significantly lower (linear; p<0.01) in supplemented rabbit groups compared to the control group according to the microbiological analysis of cecal digesta. Based on breed effect, the results indicated that Jabali rabbits (local) performed better than V-line rabbits (foreign) in the majority of the studied traits.Conclusion: Dietary propolis is promising for further investigation into improving intestinal health and enhancing immunity in growing rabbits.

Influence of strain and flock age on geometrical and mechanical attributes of eggs produced from Japanese quail birds

We investigated how the geometrical and mechanical properties of eggshell of Japanese quail are affected by strain and flock age. Two strains of quail (white and gray) were used in the current experiment. The results showed that there was no significant difference for all geometric measurements due to strain effect. Eggs produced from the older birds showed significantly higher (P < 0.01) values compared with younger age for all studied traits. Eggs produced from quails at 22 weeks had a significantly (P < 0.01) darker yolk color than that of the younger age. Superiority in shell thickness, shell weight, and breaking force was detected in eggs of gray quails compared with white quails. On the other hand, the eggs from white quails had significantly higher values for static stiffness and Young's modulus as compared with those of gray counterparts. A significant decrease (P < 0.01) was found for fracture toughness and Young's modulus in eggs of aged birds. A significant negative relationship was found between the breaking force and both static stiffness and Young's modulus. A significant positive relationship was observed between breaking force and both shell thickness and shell percentage. The phenotypic correlation between eggshell breaking force and toughness was relatively high.

Genetic diversity of Saudi native chicken breeds segregating for naked neck and frizzle genes using microsatellite markers

Objective

Recently, there has been an increasing interest in conservation of native genetic resources of chicken on a worldwide basis. Most of the native chicken breeds are threatened by extinction or crossing with ecotypes.

Methods

Six Saudi native chicken breeds including black naked neck, brown frizzled, black, black barred, brown and gray were used in the current study. The aim of the current study was to evaluate genetic diversity, relationship and population structure of Saudi native chicken breeds based on 20 microsatellite markers.

Results

A total of 172 alleles were detected in Saudi native chicken breeds across all 20 microsatellite loci. The mean number of alleles per breed ranged from 4.35 in gray breed to 5.45 in normally feathered black with an average of 8.6 alleles. All breeds were characterized by a high degree of genetic diversity, with the lowest heterozygosity found in the brown breed (72%) and the greatest in the frizzled and black barred populations (78%). Higher estimate of expected heterozygosity (0.68) was found in both black breeds (normal and naked neck) compared to the other chicken populations. All studied breeds showed no inbreeding within breed (negative inbreeding coefficient [F_IS]). The phylogenetic relationships of chickens were examined using neighbor-joining trees constructed at the level of breeds and individual samples. The neighbor-joining tree constructed at breed level revealed three main clusters, with naked neck and gray breeds in one cluster, and brown and frizzled in the second cluster leaving black barred in a separate one.

Conclusion

It could be concluded that the genetic information derived from the current study can be used as a guide for genetic improvement and conservation in further breeding programs. Our findings indicate that the Saudi native chicken populations have a rich genetic diversity and show a high polymorphism.

Effect of probiotic supplementation and genotype on growth performance, carcass traits, hematological parameters and immunity of growing rabbits under hot environmental conditions

The effect of dietary inclusion of probiotics and genetic groups on rabbit performance under hot environmental conditions was studied. A total of 80 rabbits aged 8 weeks were distributed into a completely randomized design in a 4 × 3 factorial arrangement, including four genetic groups and three concentrations of dietary probiotic (0, 200 and 400 g/t feed). The utilized probiotic contained 4 × 10⁹  colony-forming units/g of Bacillus subtilis. Jabali local breed (J), imported Spanish V-line (V) and their crossbreds (¼J¾V and ¾J¼V) were included in the current study. Final weight and body weight gain were not significantly affected by dietary probiotic levels or genetic group. The feed conversion ratio was better for purebreds than that of crossbreds. A significant improvement in percentage of dressed carcass, mid and hind parts was recorded for rabbits fed a diet containing 400 g probiotic/t feed compared with those fed a basal diet or low probiotic level. Probiotic supplementation had a significant decrease in serum cholesterol. Rabbits given 400 g probiotic/t feed had higher hemoglobin, red blood cells and platelets. Adding 400 g probiotic/t feed to rabbit's diet significantly (P ≤ 0.05) improved cell-mediated immunity compared to the other treatments 48 h post-injection.