Pregnancy loss in beef cattle: A meta-analysis.

Area of Science:

• Reproductive biology
• Veterinary science
• Agricultural science

Background:

• Pregnancy loss in beef cattle presents significant management and economic challenges.
• Understanding reproductive failure across gestation is crucial for improving beef cattle production.

Purpose of the Study:

• To conduct a meta-analysis quantifying reproductive failures in beef cattle.
• To assess losses during fertilization, early embryonic development, and late embryonic/early fetal development.

Main Methods:

• Meta-analysis of over 56,000 diagnostic records from 159 studies.
• Analysis divided into fertilization/pre-blastocyst loss (days 1-7), early embryo loss (days 7-32), and late embryo/early fetal loss (days 32-100).

Main Results:

• Significant developmental failure occurs within the first 7 days of gestation (28.4% loss).
• By day 30, 47.9% of cows are not pregnant after a single insemination.
• Late embryonic/early fetal loss (days 32-100) was 5.8%.
• Bos indicus had higher early embryonic loss than Bos taurus.
• Primiparous cows had higher early embryonic loss; nulliparous heifers had higher late embryonic/early fetal loss.

Conclusions:

• Substantial pregnancy loss in beef cattle occurs very early in gestation.
• Reproductive failure rates vary by developmental stage and cattle subspecies/parity.
• Findings provide a baseline for beef cattle pregnancy loss specific to different stages.