60,XX/60,XY CHIMERISM AND FREEMARTINISM IN HETEROSEXUAL BOVINE TWINS

In this study, 42 heterosexual bovine twins (10 co-borned couples, 19 females, and three males) were cytogenetically evaluated. These animals from several bovine breeds, mainly Holstein (17) and Brown Swiss (11), were herded in particular farms located in different regions of the State of Sao Paulo and from the Institute of Animal Science and Pastures (IZ), Nova Odessa, SP. Cytogenetic analysis were assessed in metaphases from cultured lymphocytes. The 60,XX/60XY chimerism were observed 90.5% of the animals and it varied from 1.8 to 90.2% of female cells. From all chimeric animals 3,806 cells were evaluated, among them 1,268 were XX cells (33.3%) and 2,538 were XY cells (66.7%). In nine co-borned couples, female cell rates ranged from 24.8 to 21.5% and male cell rates from 75.2 and 78.5% in males and females, respectively. In one couple, there was no evidence of cell exchange between twins with female presenting only female cells