Trials to Increase the Availability of Ovsynch Program Under Field Conditions in Dairy Cows

  • Jeong, Jae-Kwan (College of Veterinary Medicine, Chungbuk National University) ;
  • Choi, In-Soo (College of Veterinary Medicine, Chungbuk National University) ;
  • Lee, Soo-Chan (College of Veterinary Medicine, Chungbuk National University) ;
  • Kang, Hyun-Gu (College of Veterinary Medicine, Chungbuk National University) ;
  • Hur, Tai-Young (National Institute of Animal Science, RDA) ;
  • Kim, Ill- Hwa (College of Veterinary Medicine, Chungbuk National University)
  • Received : 2016.07.02
  • Accepted : 2016.07.29
  • Published : 2016.08.31


This study investigated whether presynchronization with GnRH 6 days before initiation of the Ovsynch program improved reproductive outcomes in dairy cows. Additionally, postponement of initiation of the Ovsynch program for cows during the metestrus phase by 5 days was investigated to determine if it improved reproductive outcomes. To accomplish this, 941 Holstein dairy cows with unknown estrous cycle were randomly allocated into an Ovsynch group (n = 768; $100{\mu}g$ gonadorelin [a GnRH analogue], $500{\mu}g$ of cloprostenol [$PGF_{2{\alpha}}$ analogue] seven days later, $100{\mu}g$ gonadorelin 56 h later and timed artificial insemination [AI] 16 h after) and a G6-Ovsynch (n = 173) that received $100{\mu}g$ GnRH followed by the Ovsynch program 6 days later. Additionally, 272 dairy cows with known estrous cycle (metestrus stage) received the Ovsynch 5 days later (Day 5-Ovsynch group, n = 272). The odds ratio (OR) for pregnancy was analyzed by logistic regression using the LOGISTIC procedure in SAS. The treatment group (p < 0.001) and AI season (p < 0.05) significantly affected the probability of pregnancy, whereas farm, cow parity, calving to AI interval, and body condition score had no affect (p > 0.05). The Day 5-Ovsynch group had a higher probability of pregnancy (OR: 1.71) than the Ovsynch group, while that of the G6-Ovsynch group was intermediate (p > 0.05). Cows inseminated during winter had a higher OR (1.39) than those inseminated during spring. Overall, additional GnRH treatment 6 days before the Ovsynch did not improve reproductive outcomes, whereas postponement of the initiation of Ovsynch by 5 days for cows during metestrus improved reproductive outcomes.


Supported by : Rural Development Administration


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