Appropriate chicken sample size for identifying the composition of broiler intestinal microbiota affected by dietary antibiotics, using the polymerase chain reaction-denaturing gradient gel electrophoresis technique

The bacterial microbiota in the broiler gastrointestinal tract are crucial for chicken health and growth. Their composition can vary among individual birds. To evaluate the composition of chicken microbiota in response to environmental disruption accurately, 4 different pools made up of 2, 5, 10, and 15 individuals were used to determine how many individuals in each pool were required to assess the degree of variation when using the PCR-denaturing gradient gel electrophoresis (DGGE) profiling technique. The correlation coefficients among 3 replicates within each pool group indicated that the optimal sample size for comparing PCR-DGGE bacterial profiles and downstream applications (such as identifying treatment effects) was 5 birds per pool for cecal microbiota. Subsequently, digesta from 5 birds was pooled to investigate the effects on the microbiota composition of the 2 most commonly used dietary antibiotics (virginiamycin and bacitracin methylene disalicylate) at 2 different doses by using PCR-DGGE, DNA sequencing, and quantitative PCR techniques. Thirteen DGGE DNA bands were identified, representing bacterial groups that had been affected by the antibiotics. Nine of them were validated. The effect of dietary antibiotics on the microbiota composition appeared to be dose and age dependent. These findings provide a working model for elucidating the mechanisms of antibiotic effects on the chicken intestinal microbiota and for developing alternatives to dietary antibiotics.

Research note: avian leukosis retroviral genes are not detected in geese

Genomic DNA from four strains of geese was analyzed for the presence of endogenous viral elements using a probe that can detect over 20 Rous-associated endogenous viral genes (ev genes) in chickens, as well as a probe and protocol that detects endogenous avian viruses (EAV). Southern blot analysis of genomic DNA did not reveal any ev genes in DNA of 15 geese from Chinese, Synthetic, or two Embden goose strains. Even under low stringency conditions, using a probe that covered most of the polymerase (pol) gene of the Rous-associated virus (RAV) and that revealed EAV elements in a chicken without ev genes, no viral loci were evident in goose DNA.