Determination of the best model for estimation of genetic parameters on the Fars native chicken traits using Bayesian and REML methods

Abstract

This study was conducted to determine the best model for genetic parameter estimation on the Fars native chicken traits using Bayesian and REML Methods. Studied traits were body weight at first day (BW1), body weight at eighth weeks (BW8), body weight at 12th weeks (BW12), age at sexual maturity (ASM), egg number production (EGP) and mean egg weight during 28 th ,30 th and 32 nd week ages (EGW) involving three generations 17, 18 and 19 during the years 2010 to 2012. Genetic parameters were estimated with REML method using WOMBAT software and with Bayesian approach using MTGSAM software. Based on AIC and DIC criteria, the most appropriate model was determined. Estimations of direct additive heritabilities for BW1, BW8, BW12, ASM, EGP and EGW by the best models using REML method were 0.31, 0.32, 0.29, 0.45, 0.24 and 0.22 and by Bayesian method were 0.36, 0.33, 0.30, 0.48, 0.26 and 0.25, respectively. The genetic correlation coefficients ranged from-0.709 between EGP and ASM to 0.844 between BW8 and BW12 (by Bayesian method) and ranged from-0.724 between ASM and EGP to 0.894 between BW12 and BW8 (by REML method). Generally, based on the employed criteria, the 1 st and 2 nd models can be suggested for analysis of body weight traits (BW1, BW8 and BW12), whereas for other traits (ASM, EGP and EGW), 1 st , 5 th , 4 th and 6 th models seems to be suitable for estimation of genetic parameters of the Fars Native fowls traits using Bayesian and REML Methods. The Bayesian approach recommended for estimation of genetic parameters on the Fars 432

Analysis of (co) variance components and estimation of breeding value of growth and production traits in Dahlem Red chicken using pedigree relationship in an animal model

“…The body weight and egg production had a negative relationship in PD-3 line in the present study. The negative association between body weight and egg production in chicken was documented by many authors [4,7,11,20,28]. Higher early body weight is of great importance for the onset of egg production as heavier birds mature early and lay more number of eggs.…”

“…The inclusion of one of the maternal effects either m, or am or c in the model could be enough to adjust the variation that occurred due to all the maternal effects [ 32 ]. The importance of “m” effects for early body weight was demonstrated, though the magnitude was less than that of “c” effects [ 7 , 8 ] in different chicken populations.…”

“…The estimates of h 2 determined using the animal model was more precise due to partitioning of the variance and covariance into all possible sources. The h 2 estimates of low magnitude with high precision and accuracy using the animal model were documented in the literature [ 5 , 7 , 8 , 29 ]. The variation in h 2 estimates over the time was due to the activation of various genes responsible for egg production [ 39 ] and persistency [ 40 ].…”

“…The association (r a ) between BW40 and EP40 was negative ( Table 10 ). The inverse relationship between body weight and egg production was an established fact in chicken [ 7 , 11 , 28 ]. The EM40 had a direct positive association with EP40, EW28 and EW40, while had an antagonistic relationship with ASM.…”

“…A maternal effect is a situation wherein traits are influenced by the genotype and environment of the mother. Maternal effects are important in the development and expression of the economic traits due to genetic or environmental differences between dams or by the combination of genetic or environmental differences [ 6 , 7 ]. The egg weight is a major factor contributing to maternal effects for body weight, however, others like hatch weight, incubation conditions, nutrition, etc.…”