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Design and performance of statistical process control charts applied to estrous detection efficiency
1Department of Animal Science, University of Minnesota, Saint Paul 55108, USA. devries@animal.ufl.edu
Journal of Dairy Science
|July 3, 2003
Summary
Statistical process control (SPC) charts can effectively monitor estrous detection efficiency (EDE) in dairy herds. These charts signal changes in EDE sooner than previously thought, offering valuable insights for dairy management.
Area of Science:
- Dairy Science
- Statistical Process Control
- Reproductive Management
Background:
- Statistical process control (SPC) charts are not widely adopted in dairy management for monitoring production processes.
- Estrous detection efficiency (EDE) is a critical factor in dairy herd reproductive performance.
- Traditional methods may not adequately capture real-time variations in EDE.
Purpose of the Study:
- To evaluate the utility of Shewhart and cumulative sum (cusum) control charts for monitoring EDE in dairy cattle.
- To assess the performance of SPC charts in detecting changes in EDE under various herd sizes and efficiency levels.
- To determine the average days to the first detection signal (ATS) for different scenarios.
Main Methods:
- A stochastic simulation model was used to track individual cow performance in simulated herds of 100 and 1000 cows.
- Estrous detection ratios (EDR) were calculated to monitor EDE.
- Shewhart and cusum control charts were designed using normal and binomial distributions at a target EDE of 0.65.
- Simulated EDE levels were varied (0.65, 0.55, 0.45, 0.35) to assess chart sensitivity and ATS.
Main Results:
- Cusum charts detected changes in EDE more rapidly than Shewhart charts, especially for larger herds (1000 cows) and greater efficiency drops.
- For a change to 0.55 EDE, ATS was approximately 300 days for 100-cow herds and 60 days for 1000-cow herds using cusum charts.
- For a change to 0.35 EDE, ATS was approximately 50 days (100 cows) and 11 days (1000 cows) with cusum charts.
- Chart performance was influenced by herd size, magnitude of EDE change, and design parameters like target ATS and reference values.
Conclusions:
- SPC charts, particularly cusum charts, can detect significant changes in estrous detection efficiency in dairy herds promptly.
- The timely detection of EDE changes using SPC charts suggests their potential utility for improving dairy herd reproductive management.
- Further research could optimize SPC chart design for specific dairy management contexts.