Evaluation of efficacy of selected oestrous synchronization programs depending on the functional state of the ovaries, heifers and cows of meat breed

The objective of this study was to assess the effect of progesterone concentration (P4) and ovarian structure models before initiation of different synchronization programmes on pregnancy outcomes per artificial insemination (AI) (P/AI) in beef cattle. Cattle were randomly assigned to one of three different synchronization programes (8-d PRID+7PGF&TAI, PGF 7-d Select Synch+PRID&TAI and 7-d PRID+6PGF&TAI); blood sampling and ultrasound examinations were performed before (day −7) and at initiation (day 0) of synchronizations, and during the experiment. The models were designed based on the turnover in P4 and ovarian structures at day −7 and day 0: groups of Model 1 were based on P4 (<1, 1–3.99 and ≥4 ng/ml); groups of Model 2 were based on P4 (<1 and ≥1 ng/ml) and referred to the phase of the oestrus cycle; groups of Model 3 were based on follicle (F) diameter (absent, <10 and ≥10 mm); groups of Model 4 were based on corpus luteum (CL) diameter (absent, <10, 10–20 and ≥21 mm). It was indicated that P/AI for heifers and cows were 54.6 and 55.3% in the 1st, 61.5 and 60.6% in the 2nd and 36.1% (only cows) in the 3rd synchronizations (P < 0.05), respectively. Significant effect on P/AI of Model 1 in the LH, HL, HM, HH groups (P < 0.05) was found in 2nd and of Model 4 in MA, MM, HH, LA in 1st (P < 0.05) synchronizations. So, the presence of higher P4 concentration (Model 1) and CL (Model 4) before initiation of synchronizations improves P/AI in beef cattle

Agreement of different methods for assessment of progesterone concentrations in beef cattle serum

Progesterone (P4) is responsible for the main reproduction processes. Concentration of P4 varies widely among different determination methods, and interpretation of these values may be difficult. The objective of the current study was to assess the agreement of three different enzyme immunoassays (ELISA) in relation to radioimmunoassay (RIA) of P4 concentration assessment of beef cow serum samples. Samples were collected randomly considering high (pregnant cows) and low (non-pregnant cows) P4 concentrations. Depending on the P4 assessment method, four groups were created as follows: Group 1 – direct samples assessed by ELISA, Group 2 – extracted samples assessed by ELISA, Group 3 – samples assessed by automated ELISA, and Group 4 – samples assessed by RIA. The mean progesterone concentration was 4.50 ng/mL, 1.24 ng/mL, 4.07 ng/mL and 4.39 ng/mL from Group 1 to Group 4, respectively. The mean difference (MD) between Group 1, Group 2 and Group 3 individually compared with Group 4 was −0.10 ± 1.24 ng/mL, 3.15 ± 3.58 ng/mL and 0.33 ± 1.42 ng/mL, and the 95% confidence interval (CI) for the differences (s) was from −0.99 to 0.78 ng/mL, from 0.59 to 5.71 ng/mL, and from −0.69 to 1.34 ng/mL, respectively. The confidence interval for the lower and upper limit of the agreement ranged from −4.12 to −1.05 ng/mL and from 0.84 to 3.91 ng/mL between Group 1 and Group 4, from −8.45 to 0.42 ng/ mL and from 5.88 to 14.75 ng/mL between Group 2 and Group 4, from −4.29 to −0.76 ng/mL, and from 1.41 to 4.94 ng/mL between Group 3 and Group 4. Our findings show that the best agreement with RIA was observed for Group 1 and Group 3, while the agreement in the extraction method was least accurate