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

Unveiling the Genetic Architecture of Semen Traits in Thai Native Roosters: A Comprehensive Analysis Using Random Regression and Spline Function Models

Improving reproductive traits, particularly semen quality and quantity, is crucial for optimizing poultry production and addressing the current limitations in native chicken reproduction. The aim of this study was to develop a genetic model to estimate genetic parameters guiding the selection of individual Thai native roosters. Using data collected from 3475 records of 242 Thai native grandparent roosters aged 1-4 years, we evaluated semen traits (mass movement, semen volume, and sperm concentration) over 54 weeks. A random regression test-day model incorporating five covariance functions, including a linear spline function with four, five, six, and eight knots (SP4, SP5, SP6, and SP8) and second-order Legendre polynomial function (LG2), was used to estimate genetic parameters. The results showed that the SP8 model consistently outperformed the other models across all traits, with the lowest mean square error, highest coefficient of determination, and superior predictive ability. Heritability estimates for mass movement, semen volume, and sperm concentration ranged from 0.10 to 0.25, 0.22 to 0.25, and 0.11 to 0.24, respectively, indicating moderate genetic influence on these traits. Genetic correlations between semen volume and sperm concentration were highest in the SP8 model, highlighting a strong genetic association between these traits. The SP8 model also revealed a high genetic correlation between mass movement and semen volume, supporting the potential for selecting mass movement as a predictor of semen volume. In conclusion, this study highlights the effectiveness of random regression models with linear spline functions to evaluate the genetic parameters of semen traits in native Thai roosters. The SP8 model is a robust tool for breeders to enhance the reproductive performance of native Thai chickens, contributing to sustainable poultry production systems.

Comparative Study of Phenotypes and Genetics Related to the Growth Performance of Crossbred Thai Indigenous (KKU1 vs. KKU2) Chickens under Hot and Humid Conditions

To improve the body weight and growth performance traits of crossbred Thai indigenous chickens, phenotypic performance and genetic values were estimated. Crossbred Thai indigenous chickens, designated KKU1 and KKU2, were compared. The data included 1375 records of body weight (BW0, BW2, BW4, and BW16), breast circumference at 6 weeks of age (BrC6), and average daily gain (ADG0−2, ADG0−4, and ADG0−6). A multi-trait animal model with the average information-restricted maximum likelihood (AI-REML) was used to estimate the genetic parameters and breeding values. The results showed that the body weight and breast circumference traits (BW2, BW4, BW6, and BrC6) for the mixed sex KKU1 chickens were higher than for the KKU2 chickens (p < 0.05). For the growth performance traits, the KKU1 chickens had higher average daily gain and feed intake and a lower feed conversion ratio than the KKU2 chickens (p < 0.05). The survival rates were not different except at up to 6 weeks of age, when that of the KKU1 chickens was slightly lower. The specific combining ability, heritability, genetic and phenotypic correlations, and estimated breeding values showed that the KKU1 chickens had better genetics than the KKU2 chickens. In conclusion, KKU1 chickens are suitable for development as crossbred Thai indigenous chickens for enhanced growth performance and for commercial use.

Genetic parameters of growth traits, trend of production and reproduction traits, and meat quality status of Ghagus, an indigenous chicken of India

Indigenous chickens play a vital role in providing nutritional security and economic support for the rural and tribal people in tropical countries like India. Ghagus, an indigenous chicken breed of India, was characterized for growth, production, and reproduction (fertility and hatchability) traits over different generations and for carcass and meat quality traits. Heritability, and genetic and phenotypic correlations among growth traits were estimated using mixed model least squares and maximum likelihood methods. Estimates of heritability of growth traits such as bodyweights at different age and 8-week shank length were high (0.32 to 0.39) in initial generation and moderate to high during latest generation (0.20 to 0.42). The correlations of growth traits with 40-week egg production were positive and significant (P < 0.001). There was improvement in 8-week bodyweight (559.3 ± 4.40 g) by 177 g over the generations. The average egg production up to 40 weeks over the generations was 35.66 eggs. There was also a significant (P < 0.001) increase in egg weights over the generations. The fertility (mean 89.3%) ranged from 85.2 to 92.3%. The hatchability on fertile egg set (mean 90.8%) ranged from 86.5 to 94.1% and it was improved by 3.9% over the generations. The carcass and meat quality study revealed that this breed has the lean meat, high protein, and attractive meat color with desirable meat quality characteristics. The study concluded that the Ghagus breed with self-propagation capacity has the potential to be improved as an indigenous meat-type breed to meet the ever-increasing demand for indigenous chickens' meat in the country.