Monitoring of recessive defects associated with low reproductive performance in dairy cattle in Uruguay

Abstract

Background: Most dairy cattle breeds originate show an average generational inbreeding rate of 1%, which favors the
occurrence of recessive defects associated with low reproductive performance.
Aim: The objective of this study was to monitor recessive defects associated with low reproductive performance in
dairy cattle.
Methods: To monitor bulls carrying the Holstein Friesian haplotype (HH) 1, HH3, and HH4 haplotypes, we analyzed
the records of 3,028 national and imported Holstein Friesian bulls from the 2021 updated sires’ catalog published
by “Evaluaciones Genéticas Lecheras”; and to determine the presence of these mentioned haplotypes, as well as
Jersey haplotype (JH) 1 and complex vertebral malformation (CVM), were genotype with the GeneTitan® 2,500 single
nucleotide polymorphism (SNP) bovine chip, estimate their frequencies and evaluate their impact on the fertility of
100 Holstein Friesian cows and 70 Holstein Friesian-Jersey crosses belonging to an experimental dairy.
Results: From a total of 1,468 (48.5%) bulls with genetic information from the sires’ catalog for HH1 and 1,471 (48.6%)
for HH3 and HH4, we found 90 (6.1%) carriers for HH1, 60 (4.1%) for HH3, and 6 (0.4%) for HH4, respectively. By
genotyping with the chip, we calculated the herd frequency of the mutant alleles and herd prevalence of carriers for
HH1 and CVM as q = 0.003 and 0.022; 0.59% and 4.3% (call rate >0.99), respectively. No mutant alleles were found
for HH3, HH4, and JH1 in the analyzed population. We examined reproductive data by observing the presence of CVM
and HH1 mutant alleles in repeat cows with an average of four services to achieve pregnancy.
Conclusion: This study demonstrated the presence of recessive defects associated with low reproductive performance
in the analyzed population, which can affect the health and productivity of dairy cattle. Therefore, cows and bulls
should be closely monitored through genetic testing to lower the incidence of recessive defects in dairy cattle.