Comparison of three reproductive management strategies for lactating dairy cows using detection of oestrus or synchronisation of ovulation and Fixed-Timed Artificial Insemination

Vazquez, Richard (2022) Comparison of three reproductive management strategies for lactating dairy cows using detection of oestrus or synchronisation of ovulation and Fixed-Timed Artificial Insemination. MVM(R) thesis, University of Glasgow.

Abstract

The most common dairy cattle reproductive management strategies combine oestrus detection with hormonal protocols for synchronisation of ovulation for breeding. However, approximately 50% of oestrus cycles are missed in commercial dairy farms due to human error and poor expression of oestrus behaviour. Furthermore, around 20% of cows experience prolonged postpartum anovulation. Synchronisation protocols may have variable synchronisation rates, producing suboptimal pregnancies per artificial insemination (P/AI). The aim of this study was to compare the reproductive performance of three commercial reproductive management strategies in lactating dairy cows: a combination of oestrus detection (OD) followed by ovulation synchronisation protocol for fixed timed artificial insemination (FTAI) either using Ovsynch or PRID-synch, or Double Ovsynch at FTAI. Cows (n = 1681) were randomly assigned to one of three different reproductive strategies at calving: Oestrus detection - Ovsynch (OD-Ov), Oestrus detection - PRIDsynch (OD-PR) and Double Ovsynch (DO). Cows enrolled in OD-Ov, and OD-PR were eligible to be inseminated after observed oestrus between 50 and 70±3 days in milk (DIM). Cows in which oestrus was not detected between 50 and 70±3 DIM (OD-Ov, n = 541; OD-PR, n = 562) received their respective hormonal treatments at 70±3 DIM. In these two groups, cows that returned to oestrus within the period for first FTAI (<83DIM) had more than one opportunity for AI. Cows enrolled in DO were subjected to FTAI only. Postpartum disorders were recorded between 1 and 7 DIM; and lameness, mastitis and bovine respiratory disease were recorded until first AI. Body condition score (BCS) was recoded at calving, 43±3 and 70±3 DIM. Ovarian monitoring was performed by transrectal ultrasonography (US) at 43±3 and 50±3 DIM, and at 70±3 and 77±3 DIM only for synchronised cows. Effects of treatments were assessed with multivariable statistical methods relevant for each outcome variable. Pregnancy 32±3 d after first AI was similar among treatment groups (OD-Ov = 43.2%, ODPR = 41.6%; DO = 45.7%) and proportion of cows pregnant by 83 DIM was also similar among treatment groups (OD-Ov = 46.5%, OD-PR = 46.6%; DO = 45.7%). Farm, parity, BCS at 43±3 DIM and breeding sire were associated with reproductive performance. Pregnancy loss (PL) was significantly higher in the OD-Ov (9.7%) than in the OD-PR (4.1%). In conclusion, no difference in reproductive performance among reproductive strategies was observed in this study, suggesting that reproductive performance is influenced by farm-specific factors such as oestrus detection rate and P/AI, and overall cow health.

• Item Type: Thesis (MVM(R))
• Qualification Level: Masters
• Subjects: S Agriculture > SF Animal culture > SF600 Veterinary Medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Supervisor's Name: Viora, Dr. Lorenzo and Denholm, Katie
• Date of Award: 2022
• Depositing User: Theses Team
• Unique ID: glathesis:2022-82999
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 21 Jun 2022 11:06
• Last Modified: 21 Jun 2022 11:06
• Thesis DOI: 10.5525/gla.thesis.82999
• URI: https://theses.gla.ac.uk/id/eprint/82999