The aim was to detect the presence of polymorphisms at exons 1, 2, 3 and 4 of the Spi2 gene, and evaluate a possible association between them and recurrent airway obstruction (RAO) or inflammatory airway disease (IAD) in thoroughbred horses, through single-strand conformational-polymorphism (SSCP) screening. Although polymorphism was not detected in exons 1, 2 and 3, three alleles and six genotypes were identified in exon 4. The frequencies of allele A (0.6388) and genotype AA (0.3888) were higher in horses affected by RAO, although no association was found between polymorphism and horses with either RAO or IAD.

As freqüências alélicas de sete sistemas de grupos sangüíneos e oito sistemas protéicos foram determinadas em seis rebanhos de cavalos Crioulos criados no Rio Grande do Sul, Brasil. A análise destas freqüências indicou que os rebanhos apresentaram um significativo componente devido ao isolamento (Fst = 0,0866; p<0,01) e esta diferença foi confirmada a partir do dendograma construído, utilizando-se a distância de Nei. Na medição da variabilidade genética, utilizando os 15 sistemas de tipagem sangüínea, os valores mais altos encontrados foram heterozigose média: 0.4631; número total de alelos :87 e probabilidade de exclusão de um parentesco indicado: 98%. Quando todas os rebanhos foram considerada na análise, o nível de endocruzamento (Fis) foi zero. Estes resultados indicam que os cavalos Crioulos apresentam ampla variabilidade genética.

Allelic frequencies of 7 blood groups and 8 protein systems were determined in 6 herds of Criollo horse breed raised in Rio Grande do Sul, Brazil. Analysis of these frequencies showed a significant isolation component (Fst = 0.0866; p<0.01) and construction of dendogram using Nei´s D confirmed this difference among the 6 herds. The highest values measuring genetic variability on 15 blood types were average heterozygosity: 0.4631; total number of alleles: 87 and probability of exclusion: 98%. When all herds were considered together, the inbreeding level (Fis) was zero. These results indicate that the Criollo horses have a large genetic variability.