Principal components analysis applied to performance and carcass traits in the chicken

In this study, the principal components methodology was used to analyze performance and carcass traits measured in a 3747 F2 experimental population of Gallus gallus. This technique allows us to reduce the number of variables considered in the evaluation of the animals, which may facilitate genetic programs. Performance traits were body weight at 35 and 42 days of age, and weight gain from 35 to 42 days of age; carcass traits were the following: weights of liver, heart, gizzard, wings, thighs, breast and lung. The five first principal components explained about 93.3% of the total variation, and the first component explained 66%. The first component was called 'General Weight', because the largest eigenvectors were associated with body weight at 35 and 42 days of age and liver, breast, wing and thigh weights. Heritability of the first principal component was 0.23 +/- 0.05. The genetic gain of a selection index with the first two principal components was similar to the selection index gain with 10 original traits. The principal components methodology was efficient to evaluate the total variance in this group of correlated traits, allowing a drastic reduction in the number of traits to be included in the selection index for breeding purposes.