Genetic analysis on the direct response to divergent selection for phytate phosphorus bioavailability in a randombred...

The current study was undertaken to evaluate the direct response to 3 generations of divergent selection for phytate P bioavailability (PBA) in the Athens-Canadian randombred chicken population. Cumulated divergent response (R(C)) was measured as the line difference in PBA at a given generation after adjusting for hatch and sex effects. Results showed a significant response at generation (G)1. The R(C) was unchanged from G1 to G2 and increased (1.62%) from G2 to G3 (P < 0.01) due to the application of best linear unbiased prediction (BLUP) selection in the line selected for high PBA at G2. The average BLUP estimated breeding values were used to estimate the genetic trend for the selected trait across generations. The results showed that the genetic trend was symmetric at G1 and G2 but asymmetric at G3. The application of mixed model methodology was effective in separating the environmental component from phenotypic change. When the data of the high (H) line or the low (L) line in the selected generations (G1 to G3) were combined with the data from the base population (G0), the heritability estimates for PBA were 0.07 +/- 0.02 and 0.09 +/- 0.02, respectively. The line selected for high PBA showed gain, and the line selected for low PBA showed a decrease in estimated breeding values across the generations. The results demonstrated that modest progress could be obtained by incorporating PBA into selection programs. However, other correlated traits of economic importance need to be evaluated before any decision to incorporate selection of PBA into breeding schemes be initiated.