Recessive genetic variants associated with miscarriages and calf mortality in dairy cattle

analysis of their presence and impact on the reproductive performance of Holstein Friesian cows in Uruguay

Resumo

Experiments I and II of this thesis consisted of the optimization of real-time PCR-HRM/Melting techniques for the detection of complex vertebral malformation (CVM, OMIA 001340-9913) and cholesterol deficiency (CD, OMIA 001965-9913), as well as to determine their existence in the representative sample of Holstein Friesian cows (n = 279 for CVM; n = 103 for CD) from Uruguay. The amplification of the PCR products of 79 bp of CVM and 170 and 146 bp of CD provided a clear differentiation between the two genotypes. CVM prevalence (6.45 %) was high. The BoERVK mutant insert associated with CD was not detected. Experiment II consisted of: (a) identification of bulls (n = 3028) with genetic information for haplotypes related to fertility problems causing abortions and calf mortality in dairy cattle (HH1, OMIA 000001-9913; HH3, OMIA 001824-9913; y HH4, OMIA 001826-9913) by analysis of the Holstein Friesian 2021 sire catalog; and (b) determine the presence of these haplotypes, JH1 (OMIA 001697-9913) and CVM with the GeneTitan® bovine chip; calculate their frequencies; and assess their impact on fertility in Holstein Friesian cows and Holstein Friesian-Jersey crosses (n = 170) of an experimental dairy farm. Of a total 48.5 % of bulls had genetic information for HH1, and 48.6 % for HH3 and HH4. Of these, 6.1 %, 4.1 % and 0.4 % were HH1, HH3 and HH4 carriers. Chip genotyping was performed to calculate HH1 and CVM prevalence, which were 0.59 and 4.3 %, respectively (call rate > 0.99). No mutant alleles were found for HH3, HH4, and JH1. We examined reproductive data by observing the presence of CVM and HH1 mutant alleles in repeat cows, which gave birth to dead calves, with an average of 4 services to achieve pregnancy.