Mapping gaot genetic resources of SW Chad. I. Height at the withers (HW), septh of the thorax DT and index of substernal slenderness (ISs)

Abstract

A field study was carried in Chad South-West quarter and thus covered about 20% of the national territory (over 250,000 km2) involving 60 sampling sites. The sampling ratio reached 1/440. A total of 2768 adult goats were examined to study the index of substernal slenderness (ISs), equal to substernal gap/depth of the thorax (SG/DT), with SG being equal to height at the withers minus depth of the thorax (SG = HW-DT). Plotting the 60 sites mean ISs revealed the existence of two subpopulations characterized by non overlapping histograms. Mean ISs were 1.04 and 1.50 for subpopulations 1 and 2, respectively. These biometrically defined subpopulations occupied well separated geographical areas. Subpopulation 1 was located south of latitude 11°N, in the area called zone 1 by the authors and subpopulation 2, north of that parallel, in the area called zone 2. The parting line between both zones roughly ran for 100 km along the 11th parallel within the area of study. These results confirm the discriminating power of mapping using two types of measurements only: one vital (DT, which characterizes the metabolic volume of the animal), the other morphological (ISs).