Modelling female fertility traits in beef cattle using linear and non-linear models

The effect of the Robertsonian translocation 1/29 on the fertility of beef cattle reared under extensive conditions: a 30 years retrospective study

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 analyzed the effect of rob(1;29) in a Retinta cattle breed dataset gathered during the last 30 years. The data presented herein includes 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 with 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<0.001). 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 bulls carrier as stallions. The effect of rob(1;29) in 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.