2022 – MOLECULAR GENETIC SELECTION TO REDUCE SALMONELLA TYPHIMURIUM CIRCULATIONS IN CHICKENS

Salmonella infection in chickens continues to be a major public health concern.

Among Salmonella enterica serovars, Typhimurium is the cause of severe intestinal pathology in young chicks and economic losses for the poultry industry. Additionally, S. Typhimurium could infect humans and result in an acute gastrointestinal infection. Controlling S. enterica in poultry industry is an ongoing concern for several countries around the world. Increasing the genetic resistance of chicken to salmonella by genetic selection programs, which may be carried out using phenotypic or genotypic data, is an efficient way to prevent salmonellosis. The first generations of simple crossing between Fayoumi (F) and Rhode Island Red (R) breeds and their ½F½R and reciprocal ½R½F crosses were utilized to estimate heterotic effects. Also, the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect polymorphic associations of gallinacin (Gal) genes (Gal2, Gal3, Gal4 and Gal5) with caecal bacterial count of S. Typhimurium, and IgA, IgG and IgM antibody titres in the studied populations. The chicks of each genetic group (120 birds) were infected with S. Typhimurium at 10 day of age (10^6 cfu/chick). The R breed had a significantly higher least square mean of S. Typhimurium load, followed by ½F½R cross, ½R½F cross, and F breed while, The F breed had the highest LSMs of IgA, IgG, and IgM antibody titres, followed by ½R½F cross, ½F½R cross, and the R breed. Direct heterosis estimates were significant for S. Typhimurium count and IgA antibody titre, but not for IgG and IgM antibody titres. For molecular associations, the CC genotype of Gal3 gene had a significant lower S. Typhimurium count and higher IgA and IgM antibody titres than TT genotype in R breed, while the birds of the genotype TC had lower significant S. Typhimurium count in ½R½F crossbred and significant higher antibody titres in ½F½R crossbred. In the Gal4 gene, birds with the GG genotype had a lower significant S. Typhimurium count and IgA, IgG and IgM antibody titres than birds with the AA genotype in R breed, but birds of the genotype AG had higher significant IgA, IgG and IgM antibody titers in ½R½F crossbred than the birds of GG and AA genotypes. Birds with the CC genotype of Gal5 gene had lower significant S. Typhimurium count and higher IgA and IgG antibody titers. The birds with genotype AA had lower significant S. Typhimurium count and higher significant IgA and IgG antibody titers than birds with CA genotype. This study suggested that the Fayoumi breed may be employed in breeding programs to boost immunity against S. Typhimurium in chickens, and the Gal3, Gal4, and Gal5 genes might be used as marker-assisted selection in chicken selection programs to increase S. Typhimurium resistance.