Genetic analysis of growth and egg production traits in synthetic colored broiler female line using animal model

Variance and genetic parameters were estimated for growth and production traits of synthetic broiler female line (PB-2) using REML animal model to delineate the population status, direct additive, maternal genetic, permanent environmental effects, besides genetic trends and performance of economic traits. The overall least squares mean (LSM) for body weights at 0 day (BW0), at 2 weeks (BW2), at 4 weeks (BW4), at 5 weeks (BW5), shank length at 5 weeks (SL5), and breast angle at 5 weeks (BA5) of age were 40.03 g, 207.40 g, 589.58 g, 828.51 g, 76.89 cm, and 80.78°, respectively. The overall LSM for egg production up to 40 weeks of age (EP40) and egg weight at 40 weeks (EW40) were 66.02 eggs and 58.23 g, respectively. The heritability estimates using the best model for BW0, BW2, BW4, BW5, SL5, and BA5 were 0.06 ± 0.03, 0.19 ± 0.03, 0.15 ± 0.03, 0.14 ± 0.02, 0.08 ± 0.02, and 0.02 ± 0.01, respectively. The heritability estimates were low to moderate in the magnitude for all early growth traits. The heritability estimate for egg production up to 40 weeks (EP40) was 0.30 ± 0.05. The heritability estimates for adult body weights at 20 and 40 weeks of age (BW 20 and BW 40), age at sexual maturity (ASM), and egg weight at 40 weeks (EW40) were 0.21 ± 0.04, 0.19 ± 0.04, 0.16 ± 0.03, and 0.33 ± 0.05, respectively, and the estimates were moderate to high in magnitude. Model 4 with additive, maternal permanent environmental, residual, and phenotypic effects was the best model for growth traits except for BW0 and BA5. The average genetic gain observed in primary trait (BW5) over the five generations was 13.62 g per each generation indicating effective selection. The animal model minimized the overestimation of genetic parameters and improved the accuracy of the BV, thus enabling the breeder to select the suitable breeding strategy for genetic improvement.

Differential gene expression in liver of colored broiler chicken divergently selected for residual feed intake

Feed constitutes about 60-70% of the total cost of poultry production. So maximizing the feed efficiency will reduce production cost. The rapid growth in the juvenile period is essential to achieve higher body weight. Therefore, identifying the genes and pathways involved in rapid growth at an early age with a lesser requirement of feed is of utmost importance to further economize the broiler production. The efficiency of feed utilization was measured using RFI (residual feed intake). The present study aimed to estimate the RFI (0-5 week) in a population of indigenously developed colored broiler sire line chicken as well as identifying the differentially expressed genes influencing RFI in high and low RFI groups. The liver samples of high and low RFI broiler chicken aged 35 days were used for microarray analysis. A total of 2798 differentially expressed genes (DEGs) were identified, out of which 913 genes were downregulated and 1885 were upregulated. The fold change varied from - 475.17 to 552.94. A subset of genes was confirmed by qRT-PCR, and outcomes were matched well with microarray data. In the functional annotation study of DEGs, the highest significant GO (Gene Ontology) terms in the biological process included protein transport, protein localization, regulation of apoptosis, and mitochondrial transport. Gene network analysis of these DEGs plays an important role to understand the interaction among genes. Study of the important genes which were differentially expressed and the related molecular pathways in this population may hold the potential for future breeding strategies for augmenting feed efficiency.