Metrics to assess your herd's reproductive performance
"In recent years the opinion has been held by a large number of dairymen that difficulties with breeding accompany high milk production. ...As the level of production has also increased during the same interval, the conclusion has been drawn that the two bear the relations of cause and effect." This quote is from Dr. Eckles in 1929, so the challenge of getting cows pregnant is not new. Over the past 15 years there has been an increased focus on improving reproduction. Minnesota DHI herds have increased pregnancy rates from 14% in 2000 to 17% in 2015 with over 35% of herds over 20%. The six platinum Dairy Cattle Reproductive Council award recipients this year had pregnancy rates between 32 and 39%. The way to increase pregnancy rate is to systematically evaluate reproductive performance and work with your reproductive team to develop an action plan for improvement.
First - let's understand the factors that affect pregnancy rate. Pregnancy rate is calculated by multiplying insemination risk by conception rate (not exactly correct for synchronization programs, but close). Focus on these two metrics to improve pregnancy rate. All DHI records provide these numbers. If you want to track this on a timely basis, you will need one of the dairy management software programs or ask a reproductive advisor to print it for you.
Troubleshooting insemination risk is easier than conception rate. If insemination risk is low, the major factors to exam include: heat detection, anovulatory cows, and speed of identification and re-insemination of open cows. Troubleshooting conception rates can be more of a challenge. The four major factors affecting conception rates are shown in Figure 1. Bull fertility is usually not a major issue if AI breeding is used. Technician skill should be tracked. Inseminators should regularly attend refresher courses or technique should be evaluated by a professional. Is sperm present in the reproductive tract when the ovum is ovulated? Improper timing is a function of accuracy of heat detection, interpretation of tail paint, and activity system interpretation. The hardest factor to troubleshoot is cow fertility. In my experience, this is also the most common reason for low conception. Figure 2 shows all the factors affecting cow fertility.
Excellent records are required to evaluate reproductive performance. Record the following items. DHI field supervisors will record this information if asked:
- Cow ID and insemination date
- Sire ID
- Technician ID
- Breeding code. This is a farm specific breeding code. Keep these simple, yet meaningful. Consider the following breeding codes: a) standing heat; b) specific timed AI program - may be multiple codes if this is important; c) specific timed AI resynch program; d) chalk/tail paint; e) other - but this should include limited entries. Too many codes make evaluation more difficult.
With good records, here is a systematic method of monitoring reproductive metrics in a herd:
- Set a specific goal for pregnancy rate. Every farm should have a goal of achieving at least a 20% pregnancy rate. Most farms should be aspiring for a 22 to 25% pregnancy rate. It's not easy but it pays big dividends.
- Evaluate the annual 21-day pregnancy rate. Is it going up or down?
- Evaluate the last 6 months pregnancy rate. Is it trending up or down? Are there any recent trends in insemination risk and conception rate?
- Evaluate the pregnancy rate by breeding cycle. Are any cycles much higher than others? Often first cycle rates will be the highest with synchronization programs.
- Evaluate the pregnancy rate by month of year. Are there any seasonal trends?
- Evaluate a graph of the average and distribution of days in milk at first breeding. What is the voluntary waiting period by lactation number? Are all cows getting inseminated in a timely manner? What percent of cows are not being inseminated within 21 days of the start of the voluntary waiting period?
- Evaluate a graph of re-insemination interval. How quickly are open cows being re-inseminated?
- Evaluate conception rate by technician. Don't assume that inseminators have the same skill. Re-train inseminators with low conception rates compared to others. If some inseminators are consistently breeding sub-fertile cows, they will have a lower conception rate.
- Evaluate conception rate by breeding code. Label codes and keep them to a minimum. Make sure all inseminators know the definition of the codes for improved accuracy. Too many codes make it difficult to evaluate records. I have suggested the codes above, but they must be meaningful for your farm. You can evaluate the success of new programs (such as double ovsynch) or a change in an existing program.
- Develop an action plan for improvement. There are many other metrics to monitor, but these will troubleshoot most issues on farms. Follow up regularly with your reproductive advisors to determine if your plan is successful and adjust accordingly.
Many farms have been able to maintain good reproductive performance while achieving high milk production. They have accomplished this result by developing a systematic approach to evaluating records and making management adjustments. Most herds will be able to achieve reproductive success by consistently monitoring and implementing science-based reproductive practices.