Estimation of genetic parameters for ascites syndrome in broiler chickens.

Genetic parameters for the ascites syndrome (AS) were estimated for meat-type chickens. Data had been collected over 11 generations of selection for body weight and other traits within two distinct breeds (Cornish and White Rock). Linear methods (LM) were used to estimate genetic parameters and also to analyze a binary measure of survival. Survival analyses (SA) were also conducted to estimate the effects of various factors influencing the incidence of AS by evaluating the number of days that the birds survived. The animal model was used exclusively with linear methods. Heritabilities (h2) on the liability scale were 0.12 +/- 0.02 and 0.22 +/- 0.01 in the White Rock and Cornish breeds, respectively; however, the genetic correlation (r(g)) with body weight was not possible to estimate due to the low prevalence of the defect trait studied (1.5% in the Cornish and 1.1% in the White Rock). Because males are more prone to AS, the h2 using the male records only were 0.22 +/- 0.017 and 0.41 +/- 0.009, and the r(g) were 0.35 +/- 0.007 and 0.22 +/- 0.009 in the dam and sire populations, respectively. In conclusion, the heart defect investigated was heritable and had a positive genetic correlation with body weight.