title: Genetic parameters of body weight and ascites in broilers: effect of different incidence rates of ascites syndrome.
abstract: 1. The objectives of the current study were to investigate the effect of incidence rate (5%, 10%, 20%, 30% and 50%) of ascites syndrome on the expression of genetic characteristics for body weight at 5 weeks of age (BW5) and AS and to compare different methods of genetic parameter estimation for these traits. 2. Based on stochastic simulation, a population with discrete generations was created in which random mating was used for 10 generations. Two methods of restricted maximum likelihood and Bayesian approach via Gibbs sampling were used for the estimation of genetic parameters. A bivariate model including maternal effects was used. The root mean square error for direct heritabilities was also calculated. 3. The results showed that when incidence rates of ascites increased from 5% to 30%, the heritability of AS increased from 0.013 and 0.005 to 0.110 and 0.162 for linear and threshold models, respectively. 4. Maternal effects were significant for both BW5 and AS. Genetic correlations were decreased by increasing incidence rates of ascites in the population from 0.678 and 0.587 at 5% level of ascites to 0.393 and -0.260 at 50% occurrence for linear and threshold models, respectively. 5. The RMSE of direct heritability from true values for BW5 was greater based on a linear-threshold model compared with the linear model of analysis (0.0092 vs. 0.0015). The RMSE of direct heritability from true values for AS was greater based on a linear-linear model (1.21 vs. 1.14). 6. In order to rank birds for ascites incidence, it is recommended to use a threshold model because it resulted in higher heritability estimates compared with the linear model and that BW5 could be one of the main components of selection goals.
authors.affiliation: a Department of Animal Science, Faculty of Agricultural Sciences , University of Guilan , Rasht , Iran.
authors.forename: J
authors.initials: J
authors.lastname: Ahmadpanah
authors.affiliation: a Department of Animal Science, Faculty of Agricultural Sciences , University of Guilan , Rasht , Iran.
authors.forename: N
authors.initials: N
authors.lastname: Ghavi Hossein-Zadeh
authors.affiliation: a Department of Animal Science, Faculty of Agricultural Sciences , University of Guilan , Rasht , Iran.
authors.forename: A A
authors.initials: AA
authors.lastname: Shadparvar
authors.affiliation: b Department of Animal Science, College of Agriculture , Isfahan University of Technology , Isfahan 84156-83111 , Iran.
authors.forename: A
authors.initials: A
authors.lastname: Pakdel
mesh_terms: D000818:Animals; D001201:Ascites / Q000453:epidemiology / Q000235:genetics / Q000662:veterinary*; D001499:Bayes Theorem; D001835:Body Weight / Q000235:genetics*; D002645:Chickens / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D016014:Linear Models; D008297:Male; D008957:Models, Genetic; D010641:Phenotype; D011201:Poultry Diseases / Q000453:epidemiology / Q000235:genetics*; D019655:Quantitative Trait, Heritable
keywords: Ascites; Bayesian approach; genetic parameter; linear model; restricted maximum likelihood; threshold model