Metaphase chromosomes derived from leukocyte cultures of peripheral blood were examined in 15 fertile, female, heterosexual bovine twins. Of the 15 animals, 14 contained only XX cells in cultured leukocytes while the remaining female was chimeric containing 26% XY cells. The fertile, female, bovine, heterosexual twin demonstrating XX/XY sex chromosome chimerism in cultured leukocytes supplies evidence that chorionic fusion and vascular anastomosis may occur between male and female cattle twins without production of a freemartin. Although one fertile, female, bovine, heterosexual twin expressed XX/XY chimerism, we believe the leukocyte culture technique is a valuable tool for early diagnosis of the freemartin condition. In comparison with other diagnostic aids including clinical observations, erythrocyte typing, and homograft tolerance, chromosome analysis of leukocytes is equally efficient, less expensive, and more practical for routine early diagnosis of the bovine freemartin. Blood can be sampled soon after birth for karyotyping. From leukocyte culture technique, in 3 days after initiation of the cultures the reproductive capacity of the female twin can be decided.

Metaphase chromosomes derived from leukocyte cultures of peripheral blood were observed in 299 head of Brown Swiss cattle. A Robertsonian translocation (centric fusion) was found in 31 of the animals. Estimated from this small sample 2.4% of animals of the Brown Swiss breed carry the translocation. Chromosome measurements and analysis of G-banded chromosomes proved inconclusive in identification of the homologue to the short arm of the translocation chromosome. The long arm was homologous to the longest acrocentric autosome. By C-banding, a single, small area of centromeric constitutive heterochromatin on the translocation chromosome indicated a single centromere. The translocation in Brown Swiss may be homologous to the 1/29 Robertsonian translocation in many other breeds of cattle. The translocation chromosome appeared to have segregated normally from its homologues. Aneuploid karyotypes were not observed. Analyses of breeding data failed to detect any decrease in fertility of translocation heterozygous females as compared to females of the normal karyotype. It would be premature to recommend a selection program against this translocation in Brown Swiss, but widespread use of sires heterozygous for the translocation should not be encouraged.

Chromosome preparations were made from lymphocyte cultures on 52 head of British White park cattle. A translocation chromosome was found at a frequency of 60 per cent. The translocation was concluded to be 1/27, but was assumed to be the same translocation identified as 1/29 in several breeds of European continental cattle.

Journal Article A Dicentric Robertsonian Translocation in a Dexter Cow Get access Franklin E. Eldridge Franklin E. Eldridge Professor Department of Animal Science, University of NebraskaLincoln, Nebraska 68503 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Heredity, Volume 65, Issue 6, November 1974, Pages 353–355, https://doi.org/10.1093/oxfordjournals.jhered.a108548 Published: 01 November 1974