Influence of day of postpartum breeding on pregnancy rate, pregnancy loss rate, and foaling rate in Thoroughbred mares.
Abstract: Records (years 2005-2007) were analyzed from a Thoroughbred stud farm in central Kentucky. Data from all breeding cycles of foaling mares were tabulated (3184 cycles of 2003 foaling mares bred between 7 and 163 days postpartum). A multiple logistic regression model employing Bayesian statistics was used to adjust for factors that significantly affected outcome; odds ratios (ORs) for pregnancy rate, pregnancy loss rate, and foaling rate were determined to examine the influence of day of postpartum breeding on these parameters. Mares bred before Day 22 (Day 0 = day of foaling) postpartum had a decreased OR for becoming pregnant (P < 0.05); the median OR for becoming pregnant (1.00) was not reached until Day 46 postpartum. Mares bred before Day 13 postpartum had an increased OR for pregnancy loss (P < 0.05). The median OR for pregnancy loss did not decline below 1.00 until Day 78 postpartum. Mares bred before Day 20 postpartum had a decreased OR for producing a foal (P < 0.05). The median OR for producing a foal (1.00) was not reached until Day 75 postpartum. We concluded that fertility (in terms of a higher OR for becoming pregnant and a lower OR for pregnancy loss, resulting in a higher OR for producing a foal) continued to improve in Thoroughbred mares for approximately 2.5 mo postpartum. These findings are of importance to management strategies directed at early postpartum breeding, and explain some of the reported drift in subsequent foaling dates of Thoroughbred mares, despite management practices that employ early postpartum breeding.
Copyright © 2012 Elsevier Inc. All rights reserved.
Publication Date: 2012-01-05 PubMed ID: 22225688DOI: 10.1016/j.theriogenology.2011.10.034Google Scholar: Lookup
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Summary
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This study showed that the day of postpartum breeding greatly impacts the pregnancy and foaling rates of Thoroughbred mares. It suggests that mares should be bred at least 2.5 months postpartum for optimal results.
About the Research
- The research analyzed data from a Thoroughbred stud farm in central Kentucky spanning the years 2005-2007.
- The data used included all breeding cycles of foaling mares recorded during the period, with 3184 cycles of 2003 foaling mares bred between 7 and 163 days postpartum.
Methods
- A multiple logistic regression model using Bayesian statistics was implemented to adjust for factors that significantly influenced the outcome.
- Using this model, the odds ratios (ORs) for pregnancy rate, pregnancy loss rate, and foaling rate were calculated to assess the impact of the day of postpartum breeding on these rates.
Results
- The study found that mares that were bred before Day 22 postpartum (where Day 0 is the day of foaling) had a lower likelihood of becoming pregnant.
- Mares bred before Day 13 postpartum had an increased likelihood of pregnancy loss.
- Mares bred before Day 20 postpartum had a lower chance of producing a foal.
- In terms of odds ratios, the median odds for becoming pregnant, not experiencing pregnancy loss, and producing a foal were not reached until Days 46, 78, and 75 postpartum respectively.
Conclusions
- These findings suggest that Thoroughbred mare fertility (quantified as a higher OR for becoming pregnant and a lower OR for pregnancy loss, resulting in a higher OR for producing a foal) continues to improve for approximately 2.5 months postpartum.
- The study concludes that these results are significant regarding management strategies aimed at early postpartum breeding, and could explain some of the reported drift in subsequent foaling dates of Thoroughbred mares, despite management practices that encourage early postpartum breeding.
Cite This Article
APA
Blanchard TL, Thompson JA, Love CC, Brinsko SP, Ramsey J, O'Meara A, Varner DD.
(2012).
Influence of day of postpartum breeding on pregnancy rate, pregnancy loss rate, and foaling rate in Thoroughbred mares.
Theriogenology, 77(7), 1290-1296.
https://doi.org/10.1016/j.theriogenology.2011.10.034 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA. tblanchard@cvm.tamu.edu
MeSH Terms
- Abortion, Veterinary / epidemiology
- Animals
- Bayes Theorem
- Breeding / methods
- Female
- Horses / physiology
- Logistic Models
- Male
- Odds Ratio
- Postpartum Period
- Pregnancy
- Pregnancy Outcome / veterinary
- Pregnancy Rate
- Time Factors
Citations
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