The study was conducted to determine the relationship between plasma progesterone (P4) concentration on day 6 following artificial insemination (AI) and the pregnancy rate to provide recommendations for measuring P4 concentration before embryo transfer in cows. A total of 85 cows were double AI (day 0) after being detected in natural heat by visual observation. On day 6 after AI, the blood sample was collected from the coccygeal vein to measure plasma P4 concentration by ELISA method. Pregnancy was diagnosed on the 60th day after AI by rectal palpation. The results showed that the plasma P4 concentration at day 6 after AI of the pregnant cow group (4.262±2.195 ng/ mL) was significantly higher than that of the non-pregnant cow group (3.146±2.377 ng/mL) (p<0.05). The pregnancy rate was lowest in the group of cows with plasma P4 concentration <2ng/mL, then gradually increased with P4 concentration. The pregnancy rate of cows tended to be stable when P4 concentration ≥4.0 ng/mL. The pregnancy rate of cows was highest when the P4 concentration was from 3-4 ng/mL and 5-6 ng/mL. Additionally, the pregnancy rate of cows is positively correlated with the plasma P4 concentration according to the formula P= 26.356 + 6.612* P4. In conclusion, the plasma concentration of P4 at day 6 after AI has a positive relationship with the pregnancy rate of cows.

The study was carried out to assess factors related to the odds of pregnancy for dairy cattle after treating ovarian disorders in some Northern Vietnamese provinces. A total of 449 ovarian-disordered heifers and cows were given appropriate treatments for their diseases and were diagnosed by rectal palpation with pregnant status after artificial insemination. Data collected from ruminants were analyzed by applying Binary Logistics Procedure in SAS 9.0 and three methods were utilized to test the significant level of regressive coefficients related to the factors, which included various nutritional, environmental, and management factors (locations, parities, ages, body condition scores, housing types, mineral licking block diets, rubber bedding, and categories of disordered ovaries). Based on the odds ratio, cows and heifers in Ha-Noi zone had higher odds of pregnancy than in Vinh-Phuc province (odds ratio [OR] =1.97, p<0.05). Multiparous cows were likely to get a lower chance to conceive than heifers. The odds of pregnancy for dairy cattle decreased with the increase of age, and with each month increased of age, the odds of pregnancy decreased by 1.8%. The better housing condition the dairy cattle live in, the higher pregnancy rate they get. The pregnant opportunity of the dairy cattle kept in the concrete floor house is higher than that kept in rubber floor house (OR=4.03; p<0.0001). Adding mineral licking block in their diet affected the conception odds but did not affect BCS. When the appropriate treatment was used, dairy cattle with inactive ovaries were less likely to conceive than those with cystic ovarian disease and persistent corpus luteum.