Estimation of genetic parameters for ascites syndrome in broiler chickens

Genetic parameters for the ascites syn drome (AS) were estimated for meat-t ype 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 als o to analyze a binary measure of survival. Survival analyses (SA) were also conducted to estimate the effects of various factors influencing the incid ence of AS by evaluating the number of days that the birds survived. The an imal model was used exclusively with linear methods. Heritabilities (h(2)) on the liability scale were 0.12 +/- 0.02 and 0.22 +/- 0.01 in the White Ro ck and Cornish breeds, respectively; however, the genetic correlation (r(g) ) with body weight was not possible to estimate due to the low prevalence o f the defect trait studied (1.5%, in the Cornish and 1.1%, in the White Roc k). Because males are more prone to AS, the h(2) using the male records onl y 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 conclu sion, the heart defect investigated was heritable and had a positive geneti c correlation with body weight.