Simultaneous genetic improvement in leg soundness and innovative husbandry practices should improve broiler welfare without significant adverse effects on production efficiency. That is the conclusion of new research at the University of Georgia in Athens.

A multiple trait linear-threshold model has been used by R. Rekaya of the University of Georgia and co-authors there and with Cobb-Vantress Inc. to analyse data for bodyweight, residual feed intake, breast meat yield (BMY), conformation score (CS), area (AR), tibial dyschondroplasia, valgus, varus, and rotated tibia. Leg soundness traits were considered as binary responses.

Their work was published recently in Poultry Science. At the liability scale, the model included the fixed effects of flock-week of hatch, and sex of the bird and the genetic additive effect, and the error terms as random. The random maternal effect was included in the model only for bodyweight.

A full Bayesian implementation of the model was straightforward even though large number of traits and missing records were present, report the researchers.

As expected, binary traits have the lowest heritability. Heritability ranged from 0.12 for tibial dyschondroplasia to 0.44 for BMY.

Genetic correlations between bodyweight and conformation traits were moderate to high.

Residual feed intake was negatively correlated with bodyweight (−0.15), AR (−0.13), BMY (−0.04), and CS (−0.12).

Genetic correlation between leg soundness traits were generally low and negative with the exception of the correlation between valgus and varus (−0.70) and between varus and rotated tibia (−0.39).

Genetic correlations between bodyweight, BMY, CS, and AR with leg soundness traits were in general negative and low in magnitude.

Selecting for improved leg soundness will have minimal effect on bodyweight and carcass traits, concluded Rekaya and co-authors. Furthermore, genetic improvement in residual feed intake will result in improvements in carcass traits.

Reference

^{Rekaya R., R.L. Sapp, T. Wing and S.E. Aggrey. 2013. Genetic evaluation for growth, body composition, feed efficiency, and leg soundness. Poult. Sci. 92(4): 923-929. doi: 10.3382/ps.2012-02649}