Records
A farm’s records are only as valid as the consistency and accuracy of the data that are entered. A cow’s complete history including calving date, estrus dates, body condition scores, breeding dates, technician or breeders code, and pregnancy status must be accurate to correctly access a farm’s program. Traditional measures of reproductive performance are useful for comparing a herd over time or for comparing two or more herds. However, these measures do not provide information necessary to monitor current reproductive performance. The traditional measures of reproductive performance are usually found on the herd summary sheet. Most of the data, such as calving interval, is retrospective. This lag time limits its usefulness in assessing current performance. The value of the information can be enhanced by use of cohort analysis.
The most common source of data is through the Dairy Herd Improvement Association (DHIA). Data are collected and managed by several processing centers in the United States, but it is important to recognize that differences between processing centers exist. Various DHIA processing centers report the reproductive indices in different ways and the indices are not calculated in the same way by all centers. It is important to determine how an index is calculated before the numbers are analyzed. A processing center should be contacted for the definitions used in its reports before data analysis is attempted. In the southeastern United States, many dairies utilize Dairy Records Management System (DRMS). DRMS processes dairy records in Raleigh, North Carolina and has staff in Raleigh and Ames, Iowa to provide technical support.
On-farm software systems are available to dairy producers and veterinarians to assist in the evaluation of the data. The two most common systems used by dairy producers and consultants are PC Dart and Dairy Comp 305. There is regional bias to these systems, with PC Dart almost exclusively used in the southeastern United States and is the one discussed here. Once understood, either system can effectively help “massage” the numbers to create reports, graphs and charts to evaluate the different areas of a dairy’s performance.
Guidelines to abnormal findings and parameters can be developed using the DairyMetrics© portion of DRMS. DairyMetrics© is a benchmarking tool for dairy farm performance evaluation. This service allows the veterinarian to compare a herd with other selected herds, also known as cohort herds. These cohort herds can be selected based on their individual parameters within five classifications (general, production, udder health, reproduction, and genetic information). Within these five classifications, there are 76 variables from which to choose. The DairyMetrics© program allows comparison of the means, standard deviations, minimums, and maximums of selected parameters for a herd and the cohort herds. Percentiles for each herd performance parameter in comparison to the cohort group are also given. The veterinarian has the option of graphing a herd and its cohorts for the previous 3 months and from data 1 year ago. The value of this program is the opportunity to choose the cohorts from the over 15 000 herds processed by DRMS. The database is updated nightly to maintain current herd information so data is relevant and compares a herd to those in your area, state, or region.
When reviewing the farm’s DHIA records, the DRMS 202 Herd Summary Sheet gives an overview of the dairy and contains relevant information including milk production, reproduction, genetics, udder health, and feed cost information.1 Data are normally broken down by parity (first lactation, second lactation, third and greater lactation, and all lactations). The reproduction section of the 202 Herd Summary Sheet has summary data for the current breeding herd, the total herd, and a yearly reproduction summary. The current breeding herd designation includes all cows that are past the farm’s voluntary waiting period (VWP). The VWP represents the time period from calving to first breeding. Pregnant cows included in this report should be given a “P” code and are defined as those diagnosed as pregnant or those bred 65 days or more before the current test date or before they have left the herd.
The DRMS Total Herd Reproduction Summary contains breeding and pregnancy data on all cows in the herd (including those below the VWP) and is also listed for the entire herd by parity. The only cows not included in this report are those recorded as reproductive cull cows (“C” code). In this summary, various aspects of herd reproductive management and herd performance can be seen. The report contains an area that will calculate the average days open at first service; it will show the percentage of cows bred in relation to the VWP and the calculated average days to first breeding. Delaying the first breeding will increase this number and can have a dramatic effect on the herd’s calving interval (CI). Measured in months, the CI is the period from one calving to the next. The actual CI is retrospective and better analysis may be made by comparing the actual versus predicted CI.
The other area that will affect the CI is the conception rate. In the Total Herd Reproduction Summary, it will be displayed as the number of services per pregnancy for both pregnant cows and for all cows. Services per pregnancy for pregnant cows includes the data for all pregnant cows currently in the herd and those that have left the herd within the last 9 months if recorded as pregnant. It is calculated by the number of services recorded to those cows divided by the number of pregnant cows. Services per pregnancy for all cows includes all cows with diagnosed pregnancies and/or cows not returning to heat in 65 days after breeding and also includes all cows that have left the herd within the last 9 months. This figure contains all services in this evaluation period divided by the number of pregnant cows. Services per pregnancy should be evaluated by parity and by days in milk at first breeding. It is also useful to compare services per pregnancy for pregnant cows with services per pregnancy for all cows. As with other parameters, it is important to note that the mean may not represent the herd’s reproductive success because cows with numerous services may misrepresent the actual pregnancy data.
Service or heat intervals are also included in this report. These figures vary in accuracy since all breeding and heat dates must be reported. The figures are based on all intervals for each cow and the dates of the recorded estrus or breeding. Four categories are listed in this section: less than 18 days, 18–24 days, 36–48 days, and all other intervals. Expected estrous cycles will be 18–24 days. Intervals less than 18 days can indicate reproductive problems such as cystic ovaries, inadequate heat detection (false heats), or use of prostaglandin. Intervals of 36–48 days indicate that one heat was not observed. Service or heat intervals in the “other” category are likely to be associated with two or more missed heats, anestrous cows, or those with abnormal heat cycles.
The number of services and the percentage of successful services can also be reviewed. These are reported by first, second, and third and greater services to cows and includes current breeding herd, all breedings on cows removed from the herd in the last 9 months, and all breedings on cows coded as reproductive culls. It also calculates the “service sire merit $” which is the “average merit $” for all services to proven sires. Service number and percent successful are used with the service or heat interval to see how aggressive and successful the farm is with its breeding program. The percent successful by service number can help evaluate successful programs such as timed AI protocols or pinpoint times and areas where the program may be failing.
The Yearly Reproductive Summary is a current view of the previous year’s reproductive data and is calculated using the most recent six test intervals up to 200 days from the current test date. Services on cows that have left the herd and the reproductive cull cows are also included. The chart will often include information on the month prior to the 12-month period or “month dropped.” This information is for historical review of the herd 1 year ago but is not included in the current yearly figures.
Detection of estrus is critical in herds not using a timed AI program. Success or failure of estrus observation is found in the percent heats observed data. The formula for estrus detection efficiency is shown below:
