Ovarian response to polyovulatory stimulation in Holstein cows with different polymorphic variants of the DIO1 gene

The response of the ovaries of cattle to polyovulatory stimulation is characterized by significant variability and may depend to some extent on the animal genotype. In Holstein cows with a weak superovulatory ovarian response, a decreased thyroid activity was detected on the day of insemination and one week after insemination. However, there is no information on the relationship between polymorphism of genes controlling the thyroid system and the ovarian response to polyovulatory stimulation in cattle. Objective : To analyze the relationship between polymorphic variants of the deiodinase type 1 gene (DIO1) at position 13149 and the ovarian response to polyovulatory stimulation in Holstein cows. Materials and methods . The experiments involved 37 Holstein cows of the first and second lactation, in which 2 to 9 cycles of polyovulation stimulation were studied. On the first day of insemination, the number of follicles with a diameter greater than 5 mm was recorded in each ovary using an ultrasound scanner. Seven days after insemination, the embryos were washed out and assessed, and the number of corpora lutea in both ovaries was determined. Analysis of single nucleotide polymorphism of the DIO1 gene at position 13149 was performed on DNA samples using real-time PCR. Results . The frequency of occurrence of cows with the GG, CG and CC genotypes was 48,65 %, 43,24 % and 8,11 %, respectively. A tendency towards an increase in the occurrence frequency of individuals with a large number of corpora lutea (> 6,0) on the 7th day after insemination was found in animals with the GG genotype compared to the CG genotype (55,6 % versus 25,0 %, p<0,1). At the same time, among cows homozygous for the G allele, individuals with a higher number of degenerated embryos (> 1.0) per 1 washout were more common (33,3 % versus 0 % in cows with the CG genotype, p<0.05). Concurrently, the occurrence frequency of cows with a large number of high-quality morulae and blastocysts washed out during one session (> 4,0) was slightly higher in the group with the GG genotype than with the CG genotype (33,3 % versus 12,5 %). Conclusions . The data obtained suggest that the response of the ovaries of Holstein cows to polyovulatory stimulation may partially depend on the polymorphism of the DIO1 gene at position 13149. Furthermore, they indicate that the effect of polymorphic gene variants on fertility traits in cattle should be considered in combination with the breed of animals.