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

Abstract

The Robertsonian translocation 1/29 (rob(1;29)) is the most worldwide widespread chromosomal abnormality in domestic animals. Previous studies have demonstrated its negative effect on fertility in dairy herds, but not in beef cattle extensively bred. In this study, we analysed the effect of rob(1;29) in a Retinta cattle breed data set gathered during the last 30 years. The data presented herein include rob(1;29) analysis of 11,505 cows from 251 herds, pedigree information of 24,790 animals and 67,457 calving records. Fertility was evaluated using estimated breeding values for the reproductive efficiency (Re), calculated as the percentage ratio between the number of calvings of an individual and the number expected in an optimal situation. Our results showed that cows carrying the heterozygote genotype showed a significant decrease in their Re (−5.10%, p < .001). No decrease was detected in free rob(1;29) animals and homozygous carriers. In addition, the incidence of rob(1;29) in the breed fertility was decreased to very low values after 30 years of avoiding selection of bulls' carrier as stallions. The effect of rob(1;29) on cattle fertility is only significant when the prevalence of carrier individuals is high. Selecting against the disease only by the paternal side reduced the incidence to negligible values.

Estimation of the Genetic Components of (Co)variance and Preliminary Genome-Wide Association Study for Reproductive Efficiency in Retinta Beef Cattle

“…Despite the incidence of carrier individuals in the whole population decresing during the last 30 years from 15.73% in 1992 to 1.06% in 2020, an increase was observed in Re phenotypic values in the same period. Although this increase in Re can be partially related to the decrease in the translocation rate, it may also be explained partly by other effects, such as improvements in animal management [15].…”

“…This parameter, called reproductive efficiency (Re), is estimated as the percentage deviation of the number of calvings that a cow has at each age, from the number of calvings that this cow could have had in optimal conditions. In the Retinta breed, the optimum age at first calving was considered two years and one year for the optimal calving interval [15]. It has demonstrated increased heritability and reliability in comparison with other reproductive traits in beef cattle, such as calving interval or age at first calving [16].…”

“…Of these, 25% were raised as purebreds, with the rest used in crossbreeding as a maternal line with other continental breeds, such as Charolais and Limousin, with the aim of increasing profitability by using crossbred individuals [33]. For over 40 years now, the Retinta breeders' association has not only gathered pedigree records but also a large phenotypic and environmental dataset, including birth and culling records from all the individuals enrolled in the breed [15]. For this reason, the Retinta breed is an interesting model by which to evaluate quantitative traits accurately, including those related to fertility.…”

Chromosome Changes in Soma and Germ Line: Heritability and Evolutionary Outcome

“…In cattle, a specific monocentric Rb between BTA1 and BTA29 is widespread; this single translocation has minimal impact on animal viability and fertility. Apparently, it arises in different breeding lines; furthermore, this translocation was also shown in the ancestral form, which indicates the karyotype prone to such a rearrangement [130][131][132]. In cases of partial or monobrachial homology, or in cases of numerous Rbs, the synapsis might be prolonged, leading to meiotic failure in some cells and decreasing fertility [133][134][135][136].…”

Exploring the Effects of Robertsonian Translocation 1/29 (Rob (1;29)) on Genetic Diversity in Minor Breeds of Spanish Berrenda Cattle via Genome-Wide Analysis

“…Among Spanish cattle breeds, it has been detected in the “Retinta” breed [ 12 ] and in other threatened Andalusian breeds [ 13 ]. The consequences of using breeding stock carrying the Robertsonian translocation rob (1;29) for reproductive performance are relevant, leading to losses of fertility in both sexes [ 12 ]. On one hand, carrier females are characterized by an increase in the embryonic mortality rate, while carrier sires show a decrease in fertility [ 14 , 15 ].…”