Frequency and distribution of rob(1;29) in eight Portuguese cattle breeds

Abstract

Cytogenetic investigations performed in eight Portuguese cattle breeds revealed the presence of rob(1;29) in both heterozygous and homozygous conditions in all, and five breeds, respectively, with variable percentages of carriers as follows: 41.0% in Arouquesa, 69.9% in Barrosa, 39.4% in Maronesa, 2.8% in Mirandesa, 8.5% in Marinhoa, 1.8% in Mertolenga, 21.3% in Raca Brava and 21.5% in Alentejana. CBA- and RBA-banding were performed to ascertain the chromosomes involved in the chromosome abnormality. A total of 1,626 animals were investigated. Reproductive parameters (number of calves per 100 cows) were higher in Mirandesa (80%) when compared with both Maronesa (75%) and Barrosa (70%) breeds, underlining that rob(1;29) reduces fertility in the carriers.

Chromosome Abnormalities and Fertility in Domestic Bovids: A Review

“…Another hypothesis is that the lower frequency is due to the attempt to reduce the meat breeds' diploid number from 2n = 60 to 2n = 58 to gain genetic advantages derived from this new genetic linkage between the two chromosomes. The frequency of this translocation varies among cattle breeds, reaching high values in several breeds, in particular in the Barrosa (Portugal), where the frequency of rob(1;29) carriers has been observed at 70%, of which 53.2% were heterozygous carriers (2n = 59) and 16.6% were homozygous (2n = 58) carriers [228]. This abnormality reduces fertility in the carriers due to the presence of abnormal trivalent meiotic configurations [2,229] originating in unbalanced gametes that give rise to abnormal embryos that die in early embryonic life.…”

Effect of the rob(1;29) translocation on the fertility of beef cattle reared under extensive conditions: A 30‐year retrospective study

“…1972-1976 1977-1981 1982-1986 1987-1991 1992-1996 1997-2001 2002-2006 2007-2011 2012-2016 Ho He complex series of chromosomal rearrangements producing a monocentric and stable configuration were responsible for the onset of rob(1;29) (Escudeiro et al, 2021). This stability across generations has allowed its spread worldwide (De Lorenzi et al, 2012), particularly in some small breeds of Europe, in which its prevalence is still high (Iannuzzi et al, 2008;Rodero-Serrano et al, 2013). Despite that, there is a consensus on the negative effect of this translocation on fertility in cattle; specific studies in extensive conditions are still missing.…”

Chromosome Abnormalities in Domestic Animals as Causes of Disorders of Sex Development or Impaired Fertility

“…In some beef breeds, its incidence exceeds 10% [2], while in some local breeds, e.g. in Portugal, the frequency of the carriers is above 50% [57]. Also, other types of centric fusions, involving other autosomes, were described in cattle [58].…”