MORPHO-BIOMETRICAL STUDY OF ROVE GOATS .2 . EAR LENGTH (EL) AND AURICULOTHORACIC INDEX (ATI) IN FEMALES

In a conservation flock of Rove goats based in Maure, on the Plan de S uviere, in the community of Collobrieres (Var, France), the growth cur ve for the ear length (EL) was studied in 75 females using a mathemati cal model called the monomolecular model [X=A-Be-kt]. This model corre sponds to the self inhibiting growth phase. A represents the asymptoti c value of the measurement, k is the relative growth rate and B is a c onstant of integration such that X(0)=A-B. For EL, the parameter estim ates are A''''=16.96, B''''=7.42 and k''''=3.59. We demonstrated that A'''', the ordinate for the asymptote could be taken as the practical value at maturity, that is to say, ELm=A''''=16 cm. The evolution of t he auriculothoracic index (ATI=ear length (EL)/depth of the thorax (DT )) was determined with respect to age. The value for the ordinate of t he asymptote is C'=A''''/A ''=0.49. As was shown for Fl,, it was demon strated that this asymptote Value could be used as the practical value at maturity, C'=ATI(m)=0.49. This value of ATI observed for the Rove breed is close to that observed for the small African goats found in N orthern Cameroon, but it is different from the values observed for goa ts in Chad. This underlines the interest in using the auriculothoracic index to make morpho-biometrical discriminations between different et hnic entities. A high correlation (r=0.93) between IGs and ATI was est imated for some goat breeds or populations from Africa and Europe. The introduction of another measurement, the depth of the thorax (DT) whi ch provides an estimate of an individual's metabolisable volume, made it possible to divide the goat breeds or populations into three groups : brevipes having it high PT and a low ATI (Rove), brevipes having a low value for both IT and ATI (Cameroon) and longipes that have a low PT and a high ATI (Chad). The different values determined for PT, IGs and ATI, that make it possible to differentiate the three groups, can be interpreted as selective responses by the goats to heat exposure. T he animals are exposed to progressively hotter temperatures as one goe s from the north coast of the Mediterranen to Cameroon and then to Cha d. These measurements are thus seen to follow the rules for weight and appendage length variations as a function of heat exposure which have been established by Bergman and Alien respectively.