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.

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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

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