Calving patterns in seasonal dairy herds

Area of Science:

• Dairy Science
• Animal Reproduction
• Veterinary Epidemiology

Background:

• Seasonal dairy herds rely on predictable calving patterns for efficient management.
• Variability in calving distribution impacts herd productivity and resource allocation.
• Previous studies have indicated differences in calving patterns, but detailed analysis in specific management systems is needed.

Purpose of the Study:

• To investigate and quantify calving patterns in seasonal dairy herds across two regions.
• To compare calving patterns between naturally mated and synchronized heifers in their first lactation.
• To evaluate the influence of induced calving on calving distribution.

Main Methods:

• Two field studies were conducted in Waikato and South Taranaki dairy regions.
• Calving patterns were analyzed based on the Planned Start of Calving (PSC), 282 days from the previous season's breeding start.
• Data included calving dates for lactating cows and first-lactation heifers, with comparisons between natural mating and synchronized artificial insemination.

Main Results:

• Field Study 1 showed an average interval of 22 days from PSC to mean calving date (range 15-30 days).
• In Field Study 2, naturally mated heifers had a 17.6-day interval, while synchronized heifers had an 11.0-day interval.
• Synchronized heifers showed concentrated calving (64.7% by 15 days post-PSC), unlike naturally mated heifers (61.7% by 3 weeks post-PSC). Induced calving influenced the duration of the last quartile of calving patterns.

Conclusions:

• Significant variation exists in dairy herd calving patterns, influenced by conception rates and induced calving practices.
• Heifer calving patterns are less concentrated with natural mating than expected; synchronization effectively concentrates calving.
• Standard calving pattern parameters may require adaptation for herds with high rates of induced calving or full herd synchronization.