Ascites syndrome (AS) is a metabolic disorder usually seen in broiler chicken flocks which are allowed to exhibit their maximum genetic merit for growth rate (GR). Although AS has been controlled in commercial strains using numerous direct and indirect selective breeding methods, it is still highly prevalent in the two local broiler sire lines (named S 1 and S 2) used in the current study. After successfully investigating the two sire lines for the feasibility of identifying the susceptible families from the resistant ones by applying saline drinking water to them as ascites inducing challenge (AIC) in Trial 1 (n = 386 chicks), we conducted Trial 2 (n = 464 chicks) by exposing the birds to cool ambient temperatures as AIC. The main aim of the current study was to investigate the relationship between early growth-related traits (GRTs) and AS incidence. In contrast to the current assumption about the positive relationship between rapid early GR in broilers and AS incidence, the results of the current study revealed no direct genetic relationship between these two traits at sire line level in the populations studied. There were no significant differences in early BW or GR traits between healthy and ascitic chicks (P > 0.05). The genetic correlation between the early GRTs and AS incidence were statistically significant but not merely positive in some instances. Furthermore, the moderate to high heritability estimates for the GRTs showed that there are some possibilities to improve these highly susceptible lines for both GRTs and resistance to AS, simultaneously.

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