PSVI-17 - Dissimilarities in thyroid profiles and pregnancy rates in dairy cows with different polymorphic variants of the DIO1 gene

Thyroid hormones are implicated in regulation of the reproductive function in cattle. In turn, thyroid metabolism is determined by the activity of different types deiodinases. Our research was aimed to compare post-insemination thyroid profiles and pregnancy rates in dairy cows with different SNP genotypes in the deiodinase gene of the first type (DIO1). Thirty lactating Russian Black Pied cows were synchronized using the Ovsynch protocol and artificially inseminated (AI). Blood samples from the cows were collected on Days 0, 7, 14, 21, and 33 after AI. Hormonal levels in the serum were measured by ELISA. Pregnancy was confirmed by progesterone concentrations and ultrasonography. Genetic variants for the DIO1 gene were tested by RT-PCR and polymorphism at position 13149 (NC_037330) was found. The occurrence frequency of cows with genotypes CC, CG, and GG was 43.3, 33.3, and 23.3 %, respectively. A proportion of pregnant cows in the CC group was higher than in the CG group (84.6 vs. 40.0%, P < 0.05) and tended to be higher than in the GG group (42.9%). The concentration of triiodothyronine (T3) in the blood of CC animals did not change during the studied period, whereas that in CG animals decreased between Days 0 and 14 (from 1.60±0.21 to 1.10±0.22 nmol/L, P < 0.05). Concurrently, the T3 concentration on Day 0 was 1.4 times lower (P < 0.05) in the CC group than in the CG group. Furthermore, the level of reverse T3 on Day 7 in the GG group was 1.3 times higher (P < 0.05) than in the CC or CG groups. Thus, cows with DIO1 gene CC genotype have a higher reproductive ability than cows with CG or GG genotypes, which may be due to peculiarities of thyroid profiles during the first two weeks of pregnancy. The study was supported by Russian Ministry of Science and Higher Education (0445-2021-0004).