A. M. G. Ibelli

Unraveling the associations of osteoprotegerin gene with production traits in a paternal broiler line.

Improvements on growth and carcass traits in the poultry industry have been achieved by intense selection for heavier chickens at early ages. This faster growth has caused serious problems due to insufficient skeletal structure development needed to support the musculature of modern broilers. The osteoprotegerin gene (OPG), located on GGA2, is an important regulator of bone metabolism and reabsorption, being suggestive as a possible functional candidate gene associated with bone integrity in chickens. This study reports associations of a single nucleotide polymorphism (SNP) in the OPG gene with production traits in a parental broiler line. Different phenotypic groups were evaluated: performance, carcass and skeletal traits. SNPs were identified within the OPG gene and the most informative SNP g.9144Cu2009>u2009G was chosen for association analyses. Chickens (nu2009=u20091230) were genotyped using PCR-RFLP. The association was carried out with QxPaK v4.0 software using a mixed model including sex, hatch and SNP as fixed effects, and the infinitesimal and residual as random effects. The OPG SNP was associated with important traits as body weight at 21xa0days, weights of tibia and drumstick skin, leg muscle yield, and tibia breaking strength (Pu2009<u20090.05). Associations were explained by the additive effect of the SNP and the additive effect within sex. This SNP could be considered a potential marker to improve bone resistance in chickens; however, caution should be taken because of its negative effect in other important traits evaluated in this study. Furthermore, these findings suggest a possible involvement of the OPG gene in fat deposition in poultry.

Environmental factors on virulence of Aeromonas hydrophila

Aeromonas hydrophila are known for being opportunistic pathogens, harboring various virulence factors and triggering lesions and death in fish. The disease caused by bacteria can make fish inappropriate for human consumption, besides representing a risk to public health. The pathogenesis can be influenced by environmental variables, affecting fish productivity and mortality. The present study aimed to determine whether A. hydrophila harbor the virulence genes aerolysin, hydrolipase, elastase, lipase, cytotonic enterotoxin (ast), lateral flagellum (laf), and polar flagellum (fla) and to evaluate the influence of environmental variables on in vitro growth, in vivo virulence and expression of some of these genes. Polymerase chain reaction (PCR)-based screening for the presence of these virulence genes was performed on 35 isolates. Six isolates containing different profiles of virulence genes were tested for in vitro growth under different conditions of pH, temperature, and ammonia and for in vivo virulence under these same environmental conditions. RT-qPCR was used to quantify the expression of aerolysin, lipase, and fla genes. All the tested environmental factors influenced the growth of A. hydrophila, while pH and ammonia concentrations influenced the bacterial virulence. The expression of the fla gene increased when bacteria were grown in higher ammonia concentration. The mortality established by Aeromonas is influenced by several environmental factors pinpointing the importance of its control in fish farming to avoid higher economic loses associated to bacterial disease outbreaks.