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GENETICS |
* Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University, Rehovot 76100, Israel; and Be’er Tuvia Regional Poultry Disease Laboratory, Be’er Tuvia 83103, Israel
1 Corresponding author: cahaner{at}agri.huji.ac.il
The rapid growth of modern broilers is associated with enhanced appetite and high metabolic rate and, consequently, high O2 demand. Ascites syndrome (AS) develops in individuals that fail to fully supply the increasing demand for O2 in their bodies under ascites-inducing conditions (AIC) such as high altitude or low temperatures. The tendency of broilers to develop AS is heritable, but efficacious selection against AS susceptibility (without affecting the normal expression of other important traits) requires identification of indirect selection criteria. In the present study, divergent AS-susceptible (AS-S) and AS-resistant (AS-R) lines were developed to confirm the heritability of AS and to facilitate future detection of criteria for indirect selection against AS susceptibility. The base population consisted of 85 sire families with a mean of 73 progeny per sire, reared in a commercial broiler house under low-challenge AIC (cold environment and pelleted feed). Chicks dying with AS manifestations were designated AS-susceptible, whereas the surviving birds were designated AS-resistant. By the end of the trial (d 48), AS mortality had accumulated to 17.2%, but AS incidence per family (%ASF) ranged from 0 to 49%, with a high heritability (0.57). Parents of 7 families with very high %ASF produced the first generation (S1) of the AS-S line, and parents of 7 families with very low %ASF produced the S1 of the AS-R line. The S1 males and females reproduced generation S2 of the selected lines, whereas additional S1 males were tested under high-challenge AIC (individual cages, cool wind, and pelleted feed). Progeny testing under this high-challenge AIC, followed by sib selection, was repeated in generations S2 and S3, resulting in a divergenceof 86.6% in the incidence of AS between the AS-S (91.3%) and AS-R (4.7%) lines. The rapid genetic divergence, and family analysis of %ASF suggested that a single or few major genes are responsible for the difference between the 2 selected lines. These lines may facilitate more sensitive and effective genomic research aimed at detecting these genes or identifying the primary physiological cause of AS.
Key Words: ascites • broiler • heritability • divergent selection • progeny testing
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