Predicted response in food conversion ratio for growth by selection on the ratio or on linear component traits, in a...

Area of Science:

• Animal Breeding and Genetics
• Quantitative Genetics
• Poultry Science

Background:

• Selection for live body weight (LWT) is common in broiler breeding.
• Food conversion ratio (FCR) is a critical trait for economic efficiency.
• Sequential selection schemes are often applied to balance multiple breeding objectives.

Purpose of the Study:

• To compare direct versus indirect selection for FCR after LWT selection.
• To investigate the impact of including LWT in selection indices on FCR response.
• To assess the robustness of statistical methods to non-normality in FCR data.

Main Methods:

• Selection index methodology was used to evaluate different selection strategies.
• Comparison of single-step and sequential selection schemes.
• Restricted Maximum Likelihood (REML) was employed for (co)variance component estimation, including for log-transformed FCR.

Main Results:

• Relative responses in FCR and aggregate genotype (H) were similar for direct and indirect selection.
• Significant differences in FCR response (5-12%) occurred with unequal heritabilities or high correlations between component traits.
• Including LWT in the aggregate genotype partially or fully offset losses in FCR response.
• REML demonstrated robustness to non-normality in FCR data, even with varying coefficients of variation.

Conclusions:

• The choice between linear index and ratio selection for FCR depends on trait heritabilities and correlations.
• Including LWT in selection indices can mitigate negative impacts on FCR response.
• REML is a reliable method for estimating genetic parameters for FCR, even with non-normal data.