Résumé:
The objective of this study was to analyze the variation of the beak shape in laying hens (ISA
BROWN) by the geometrical morphometric (MG) technique based on the reference points. In
this work, the shape of the beak in the chicken was analyzed for the first time in Algeria by
the use of modern morphometric techniques based essentially on the reference points that are
part of the MG. A total of 100 photographs were made on the beak of chickens, after
comparing with 65 chicken flesh Cobb500 strain.
The digitization of the images using the tpsDig software made it possible to retain 9
homologous reference points on the upper mandible of each beak. The Procrust overlay
method was applied using the MorphoJ software to suppress the size effect and obtain the
different configurations of the beak compared to the average "consensus" shape.
Principal Component Analysis (PCA) allowed us to extract 3 components together accounting
for 82.04% of the total change in beak shape. The other multifactorial tests applied (AFD
Discriminant Factor Analysis and the Hotteling test) revealed a very highly significant
difference (p <0.0001) between the Isa Brown and Cobb500 strains for the bill shape. More
generally, the method of landmarks applied here in a 2-dimensional framework, via the
Procrustean analysis has proved extremely effective and accurate to identify and visualize the
conformations of the beak in the chicken. The results obtained need to be confirmed by other
studies, especially on local breeds, to see how it would be possible to select animals with
beaks that are better adapted to the farming conditions of tomorrow.
