7th World Congress on Genetics Applied to Livestock Production, August 19-23, 2002, Montpellier, France HERITABILITY ESTIMATES FOR BIOMETRIC MEASURES OF THE PANTANEIRO HORSE C. McManus 1 , M. Miserani 1 , S.A. Santos 2 , J.A. Silva 3 , A.S. Mariante 4 , U. Abreu 2 , M.C. Mazza 2 , J.R. Sereno 2 1 FAV, Universidade de Brasília, 70.910-900, Brasília, DF, Brazil 2 EMBRAPA Pantanal, Rua 21 de Setembro, 1880, Bairro Nossa Senhora de Fátima, 79320-900, Corumbá, MS, Brazil; 3 Associação Brasileira de Criadores do Cavalo Pantaneiro, Rua Joaquim Murtinho s/n Poconé- MT, Brazil; 4 EMBRAPA Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil INTRODUCTION The Pantanal is a vast floodplain, situated in the center-west region of Brazil, and characterized by distinct rainy and dry seasons. In this region, beef cattle are the main economic source of income. The Pantaneiro horse is well adapted to the bioclimatic conditions of this region, and become an important economic and social factor, both for the cattle industry and regional transportation (Santos et al., 1992). The Pantaneiro horse had its probable origin from Iberian horses introduced by Spanish settlers, specially in the 16 th and 17 th centuries, and by portugueses settlers in the 18 th century (Santos et al., 1992). As a consequence of natural selection for more than two centuries, with little or no human interference, an animal well adapted to the environment appeared. At the end of the 19 th century, the population of the breed was severely reduced mainly due to Peste das cadeiras (Trypanossomiasis). Later, other menaces to survival appeared, mainly indiscriminate crossbreeding and more recently Infectious Equine Anemia (AIE). Only in 1972, with the creation of the Brazilian Pantaneiro Horse Breeders Association (ABCCP), was the breed standardized through by uniting the different phenotypes. The ABCCP still has an open book for the registration of horses. In the Pantanal, there is an estimated population of 119.000 horses, mainly crossbred animals. Of these, there are about 1600 mares and 300 males registered in the ABCCP, and the bulk of these are in the Poconé sub-region, whose breeders collaborated in the creation of the ABCCP. ince the endangered status of animal breeds is determined by the size of breeding stock (Bodó, 1990), the Pantaneiro horse is classified as vulnerable, and measures must be taken to prevent a further decrease in the population. This work carries out the first estimates of heritabilites and genetic correlations between biometric measures taken on these horses at registration. MATERIAL AND METHODS Data from 2035 animals were used, registered in the genealogical registration book of the Brazilian Pantaneiro Horse Breeders Association (ABCCP) in the period from 1972 to 2000. Fifteen linear measures (withers height, back height, croup height, midback height, head Session 05. Horse breeding Communication N° 05-18