There is no single metric that fits every farm’s goals, and there is no single metric that covers every aspect of any farm. This guide includes explanations of common measures of dairy cow reproductive performance. Use it to evaluate your farm and choose the metrics that will help you reach your goals. Dairy Records Management Service (DRMS) averages, normal ranges, * and target values, are included for reference.
Days in Milk – This the average number of days since calving for all of the cows in the herd. It is relevant as a snapshot of the status of the herd today. It is not an accurate measure of reproductive performance over time, because it tends to vary seasonally. If cows don’t get pregnant because of hot weather during July and August, days in milk will trend higher in April and May. If conception rates recover in October, days in milk will begin to trend lower in July. If days in milk are too high, we need to look to other metrics to get more insights. In robot barns, days in milk helps set expectations for the herd today. If days in milk is seasonally high, expect lower visits and more fetch cows. Average – 174; Normal Range – 157-191; Low – 123; Target 150
Conception Rate – This tells us how many of the cows that were inseminated became pregnant. It is affected by cow health, timing of insemination, heat detection, semen quality, semen handling, semen placement and more. Conception rate can be more useful if it is applied to specific groups such as, number of lactations, stage of lactation, month of the year, insemination technician, or sign of heat. Average – 40%; Normal Range – 29-51%; Target – 45%
Insemination Rate – This is the percent of cows were eligible to be inseminated that actually were inseminated. It doesn’t tell us how many cows became pregnant. It does tell us how many cows had an opportunity to become pregnant. Service rate and submission rate are other terms for the same thing. The heat detection rate is a little different because it may include cows that were detected in heat but not inseminated. Synchronization programs are the most effective way to improve submission rate. Activity monitoring systems can improve the insemination rate as compared to visual observation. Insemination rate might be lower if an activity system replaces an aggressive synchronization protocol. Average – 67%; Normal Range – 48-86%; target 65%
Eligible Cow – Cows are eligible to breed if they have passed the voluntary waiting period and they are neither pregnant nor designated to be culled. Promptly designating cows as cull cows, when it is clear they will leave the herd, decreases the number of eligible cows.
Voluntary Waiting Period – The period of time after calving during which producers choose not to inseminate cows. Voluntary waiting periods can be extended as cows maintain production longer and as producers become more confident that cows will become pregnant. Average – 60; Normal Range – 53-67; Target – Varies by farm.
Pregnancy Rate – This is the percent of the cows that were eligible to become pregnant that did become pregnant in a given time period (usually 21 days). Pregnancy rate combines conception rate with insemination rate to answer 2 questions. Were enough cows inseminated? Did enough of the inseminated cows become pregnant? The end of the voluntary waiting period is the starting line for pregnancy rate. Pregnancy rate measures how quickly cows became pregnant after the starting line. If pregnancy rate is low, it is usually easier to increase the insemination rate than it is to increase the conception rate. Synchronization programs which result in cows being inseminated immediately after they become eligible are the most likely way to improve the pregnancy rate. Average – 22%; Normal Range – 16-28%; Target – 30%
Percent pregnant by 150 DIM – This is somewhat self-explanatory. While pregnancy rate measures how quickly cows became pregnant after the starting line (voluntary waiting period), percent pregnant measures how many cows got pregnant before the “finish line.” Some producers are becoming more interested in using activity systems to find natural heats for first service. Others have extended the voluntary waiting period because cows maintain milk production longer in late lactation. Still others adjust the voluntary waiting period for individual cows or groups of cows. All of these strategies make the starting point less significant. The focus shifts to the end point. In these situations, when we start is less important, as long as cows are pregnant by the deadline – 150 days in milk. Average – NA; Normal Range – NA; Target – 50 to 80%
Pregnancy Hard Count – This is the number of pregnancies generated in a given time period. Is the program generating enough calves to maintain herd size? Can sexed semen or beef semen be used to adjust the number of heifers associated with the number of pregnancies? Will the number of pregnancies overwhelm the calf or heifer facilities? Work with your management team to develop a goal. Hard count is a very important planning tool, but it will be different for every farm. It may change seasonally, or over time, as goals change.
Percent Pregnant at Herd Check – This is a commonly quoted number because it is easily calculated in your head after herd check. It doesn’t tell anything about the cows that were not checked. If heat detection is very good, open cows might be reinseminated and not presented for herd check. In that case, the percent pregnant at herd check might be very high, but the hard count is too low. As a rule of thumb, the percent pregnant at herd check is a close approximation of the heat detection rate. If 60% of the cows are found pregnant at herd check, then the insemination rate will be close to 60%.
Cow Corner can help you choose the right metrics for your farm. I can also help you find these metrics in your herd management software. The Cow Corner program includes a monthly report with many of these measures, in an easy-to-read format.
DRMS Dariymetrics; https://www.drms.org/Reports-Data-Tools/DairyMetrics; US Holsteins, 50-1000 cows; 10/16/23
*Normal range equals 1 standard deviation, which includes about 68% of the values.
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