Characterizing pregnancy losses in lactating Holstein cows receiving a fixed-timed artificial insemination protocol

Area of Science:

• Reproductive physiology in dairy cattle
• Animal science and tropical agriculture

Background:

• Lactating Holstein cows in tropical environments experience significant pregnancy losses.
• Early pregnancy diagnosis and monitoring are crucial for herd productivity.

Purpose of the Study:

• To assess pregnancy losses from day 31 to calving in lactating Holstein cows under tropical conditions.
• To determine if serum haptoglobin and pregnancy-associated glycoproteins (PAGs) concentrations differ based on pregnancy loss events.

Main Methods:

• 708 primiparous and 844 multiparous cows underwent ovulation synchronization and fixed-time artificial insemination.
• Pregnancy status was monitored via ultrasonography on days 31, 62, 120, and at calving.
• Serum samples were collected on day 24 and day 31 (for pregnant cows) to measure haptoglobin and PAGs.

Main Results:

• Overall pregnancy losses were higher between days 31-62 (12.8%) and day 120 to calving (12.1%).
• Multiparous cows exhibited greater pregnancy losses than primiparous cows during these periods.
• Lower serum PAGs on day 31 and higher serum haptoglobin on day 24 were associated with subsequent pregnancy loss.

Conclusions:

• Pregnancy loss is a significant issue in tropical dairy herds, particularly in multiparous cows.
• Serum PAGs and haptoglobin levels in early gestation may serve as biomarkers for predicting pregnancy loss in Holstein cows.