Biometric variability of goat populations revealed by means of principal component analysis

Luanna Chácara Pires,João Batista Lopes Da Silva,Timothy A Olson,Robledo Almeida Torres,Adriana Mello Araújo,Théa M Medeiros Machado,Márcio Da Silva Costa

doi:10.1590/s1415-47572012005000072

Abstract

The aim was to analyze variation in 12 Brazilian and Moroccan goat populations, and, through principal component analysis (PCA), check the importance of body measures and their indices as a means of distinguishing among individuals and populations. The biometric measurements were wither height (WH), brisket height (BH) and ear length (EL). Thorax depth (WH-BH) and the three indices, TD/WH, EL/TD and EL/WH, were also calculated. Of the seven components extracted, the first three principal components were sufficient to explain 99.5% of the total variance of the data. Graphical dispersion by genetic groups revealed that European dairy breeds clustered together. The Moroccan breeds were separated into two groups, one comprising the Drâa and the other the Zagora and Rhâali breeds. Whereas, on the one side, the Anglo-Nubian and undefined breeds were the closest to one another the goats of the Azul were observed to have the highest variation of all the breeds. The Anglo-Nubian and Boer breeds were similar to each other. The Nambi-type goats remained distinct from all the other populations. In general, the use of graphical representation of PCA values allowed to distinguish genetic groups.

Highlights

Geographic isolation over time, along with small population size and the consequences of natural and artificial selection in domesticated animals, have contributed to the appearance of a large variety of genetic types within species, sometimes called breeds
Sahelian goats from the Western Sahara and their crosses entered Brazil by way of the Cape Verde Islands, where they had been previously introduced by the Portuguese
Whereas other groups characteristic ally had average-sized to long ears

Summary

Introduction

Geographic isolation over time, along with small population size and the consequences of natural and artificial selection in domesticated animals, have contributed to the appearance of a large variety of genetic types within species, sometimes called breeds. These same factors have contributed to variation within the breeds themselves (Hall and Bradley, 1995; Bruford et al, 2003). The standard procedure used in Brazil for defining a goat breed is first there cognition of a standard population phenotype by the Ministry of Agriculture, followed by its registration with the Goat Genealogical Registration Service (Brasil, 1977) This definition of breed, a group of animals with standardized qualitative characteristics, was developed in England during the eighteenth century (Audiot, 1985; Sierra Alfranca, 2001). Andrade (1982) stated that the introduction of goats and other livestock species to Brazil coincided with the arrival of the first African slaves

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