Genetic Parameters for Body-Weight Traits of a Native Poultry Breed in Thailand

The heritabilities and genetic correlations for body-weights measured at day-old (BW1D), and at 4 (BW4), 8 (BW8), 12 (BW12), 16 (BW16), 20 (BW20) and 24 (BW24) weeks of age, and also at first egg (BWFE) of Thai native chickens (Lueng Hang Kao Kabinburi, LHKK) were estimated using Restricted Maximum Likelihood (REML) procedures. Data were from the Kabinburi Livestock Research and Breeding Center, Thailand and the records contained five generations of performance records on 11,588 birds born from 2003 to 2007. Estimates of heritabilities for additive genetic effects of body-weight traits ranged from 0.10 to 0.51. Heritabilities for maternal genetic effects ranged from 0.04 to 0.25, except for BWFE, which had no significant maternal genetic effects. Significant maternal permanent environmental effects were observed for all traits, except for BW24 and BWFE. Estimates of additive genetic correlations between the body-weight traits ranged from 0.25 to 0.99. Estimated heritabilities and genetic correlations between body-weight traits suggest that the growth performance of LHKK chickens can be improved by selection on one or more juvenile weight traits

Genetic Associations Between Early and Late Growth with Sexual Maturity in Thai Native Chickens

The associations between early and late growth rates with sexual maturity of Lueng Hang Kao Kabinburi (LHKK) native chicken in Thailand were explored. Five generations of data from 2003 to 2007, involving 11,588 chickens, were collected at Kabinburi Livestock Research and Breeding Centre (KLRBC). Body weight measured from day-old (BW1D) to 24 weeks of age at 4 weekly intervals of 4 (BW4), 8 (BW8), 12 (BW12), 16 (BW16), 20 (BW20), 24 (BW24) weeks, and sexual maturity traits, age at first egg (AFE) and egg weight at first egg (EWFE), were recorded. The growth rates were grouped into 5 categories: BW1D to BW8 (Growth_1), BW4 to BW12 (Growth_2), BW8 to BW16 (Growth_3), BW12 to BW20 (Growth_4), and BW16 to BW24 (Growth_5). Growth_1 to 3 represented early growth and Growth_4 and 5 represented late growth. Genetic correlations were estimated between early and late growth rates against AFE and EWFE using Restricted Maximum Likelihood. Growth_1 had a favourable genetic correlation of -0.15 with AFE and a high positive (favourable) genetic correlation of 0.42 with EWFE. Growth rate between Growth_4 and Growth_5 had unfavourable genetic correlations of 0.08 and 0.30, respectively, with AFE, and favourable genetic correlations of 0.28 and 0.31, respectively, with EWFE. This study indicated that selecting for higher growth rate between day-old to 8 weeks of age would also improve sexual maturity by reducing the AFE and increasing the EWFE of LHKK chicken in Thailand

Using random regression models to estimate genetic variation in growth pattern and its association with sexual maturity of Thai native chickens

Genetic (co)variances and parameters between body weights (BW) across the growth trajectory were estimated using a univariate random regression (RR) animal model. The effect of growth rates (GH) on age at first egg (AFE) and egg weight at first egg (EWFE) were explored using a series of univariate and bivariate analyses.Body weights were taken from Thai native chickens at hatch day to 168 days of age. The model included interactions between age with hatch nested within year and sex as fixed effects, and random effects of direct additive genetic, direct permanent environmental, maternal genetic and maternal permanent environmental effects. All random effects were fitted as regressions to animals’ age via quadratic Legendre polynomials and fitting six classes of residual variances was identified as an optimal variance structure to estimate parameters.Genetic and phenotypic variances for BW increased with increasing age. Estimated heritabilities for direct additive (h2 a) and maternal genetic (h2 m) effects on BW traits ranged from 0.34 to 0.54, and 0.04 to 0.06, respectively. Estimated variance ratios for direct (c2 ape) and maternal permanent environmental (c2 mpe) effects ranged from 0.19 to 0.48 and 0.10 to 0.12, respectively. Estimated correlations between weights at different ages were high for all random effects.Estimated h2 a for six GH traits ranged from 0.06 to 0.28, while for AFE and EWFE these were 0.24 and 0.16, respectively. Estimated h2 m and c2 mpe were low for GH. Estimated genetic correlations between GH and AFE ranged from −0.22 to 0.02 and, between GH and EWFE, ranged from −0.05 to 0.40. These estimates suggested that selecting high GH chickens at 28 days of age can be expected to reduce AFE and to increase EWFE