Factors influencing multiple ovulation in dairy cows from Latvian brown, Latvian blue, and Danish red breeds at risk in Latvia

•Multiple ovulation and embryo transfer can be used to preserve and renew several local dairy breeds at risk of extinction.•A successful response to the MO treatment (3 or more corpus luteum) was observed in 24 cows (80%).•A higher serum progesterone level at the beginning of MO treatment can be used as a marker of successful multiple ovulation. The aim of this study was to determine the general factors that influence multiple ovulation (MO) in the donor cows from the breed Latvian Brown (LB), Latvian Blue (LBl), and Danish Red (DR) using a follicle-stimulating hormone (FSH) or equine chorion gonadotropin (eCG). The 30 cows aged 2 to 15 years were selected for MO and embryo flushing (EF) from the database of the Agricultural Data Center of the Republic of Latvia, of which 13 were LB cows, 7 were LBl cows, and 10 were DR. Serum biochemistry parameters and serum progesterone (P4) concentrations were determined in the donor cows on the day of starting MO treatment (time point T1). Serum P4 detection was repeated at 4 additional time points: before injection of prostaglandin F2 alpha (PGF2α) (T2), on the days of the 1st and 2nd artificial insemination (AI) (T3 and T4), and the day of EF (T5). On the day of EF, ovaries were examined by ultrasonography, and the success of MO was assessed according to the number of corpora lutea (CL). On average, 7.7 (range 1 – 19) CL were found per cow. A successful response to the MO treatment (CL≥3) was observed in 24 cows (80%). The cows that failed to respond to MO treatment were equally distributed among cow breeds. The P4 concentration of the donor cows with a successful response to MO treatment was significantly higher than in cows without the response at T1, T2, and T5. The results of multivariable negative binomial regression showed that the number of CL was positively influenced by P4 level, phosphorus, and cholesterol concentration in the blood serum before MO treatment. It was concluded that cows from breeds LB, LBl, and DR at risk in Latvia effectively responded to MO treatment.