SOFTWARE USERS NEWSLETTER
A PUBLICATION OF MINNESOTA DHIA	July  2004

Scout users who have recently updated their program by going to their Help menu and choosing "Check VAS web site for updates" may have noticed an addition called "Pregnancy Risk" to the bottom of the Rpr+Cul menu. Dairy Comp users access the same report by choosing BREDSUM option E—"21 day heat trial".

The "Pregnancy Risk" report is fast becoming an industry standard in evaluating overall reproductive efficiency in dairy herds. In the past many dairymen and consultants have used "Average Days Open", or "Projected Calving Interval" to evaluate reprodu ction. While both of those numbers have value for individual cows, and even for the herd as a whole over extended periods of time, they are not useful in evaluating current reproductive performance.

For example: How well does a change in days open reflect recent performance?

If we consider a 3 cow dairy:

Cow 1 is pregnant to a breeding at 90 DIM and is milking 200 days.
Cow 2 is pregnant to a breeding at 110 DIM and is milking 200 days.
Cow 3 is open to a breeding at 130 DIM and is milking 200 days.

What is the average DOPN? We don’t know how many DOPN cow 3 will be until she is confirmed pregnant, so the current average just includes cows 1 (90 DOPN) and 2 (110 DOPN) for an average of 100 DOPN.

If Cow 3 becomes pregnant to a breeding at 160 DIM, her DOPN can be calculated into the average: 90 + 110 + 160 = 360; 360/3=120. So average DOPN has gotten worse, even though a positive thing has happened in that cow 3 became pregnant. Using "Average Calving Intervals" can result in similar misinterpretations of current reproduction performance.

The same group of cows can be evaluated using the "Pregnancy Risk" report. We will assume a volunteer waiting period (VWP) of 50 days, and that each cow is eligible to become pregnant 1 time during each 21-day period once she reaches her VWP. The following chart shows how many cycles she is eligible in based on her DIM.

Cow 1 is pregnant to a breeding at 90 DIM, or 2 cycles
Cow 2 is pregnant to a breeding at 110 DIM, or 3 cycles
Cow 3 is open to a breeding at 130 DIM, or 4 cycles

There are currently 2 pregnancies / 9 cycles, which equals a 22% Pregnancy Rate.

If cow 3 becomes pregnant at 160 DIM a new pregnancy rate can be calculated.

Cow 1 is pregnant to a breeding at 90 DIM, or 2 cycles
Cow 2 is pregnant to a breeding at 110 DIM, or 3 cycles
Cow 3 is pregnant to a breeding at 160 DIM, or 6 cycles

Now there are 3 pregnancies / 11 cycles for a 27% Pregnancy Rate. This method shows a positive change when cow 3 became pregnant. If a herd has been having reproduction problems and makes management changes that improve repro duction, their average DOPN and Calving interval will improve over time. However, as seen in the examples above, the "Pregnancy Risk" report is much more useful in evaluating current reproduction management practices and changes.

The default information for BREDSUM\E includes heat detection and pregnancy rates for adult cows (LACT>0) over eighteen 21 day periods (378 days). Breedings which are reflected in the report include AI breedings, and natural service breedings when the breeding is recorded by a bull name (Ex. HANK). (If option 4—"Bull /Unknown" was used when recording the breeding, or BULL was entered as the Sire when recording a Pregnancy to Previous breeding, those breedings will not be included in this rep ort).

The BREDSUM\E report has been changed slightly a number of times by Valley Ag Software. Depending on the Release date for your program, the report you create may be slightly different then the one shown in this newsletter. For example, displaying the number of Aborts is a recent addition. To check your release date—go to Help, then About. See the newsletter section below about ILOOP for more information about updating your program.

The term "Pregnancy Rate" is defined as the probability (or "risk") that an eligible, open cow will become pregnant within a 21-day period.

In order for a cow to be eligible, she must be:

• Past the VWP (default VWP = 50 DIM) at start of period.
• Known to be open at start of period.
• Not marked as a "Do Not Breed" prior to or during this period.
• Present at the end of the 21 day period (i.e., not sold).
• If inseminated before or during period, has known outcome (conceived or open).

In the majority of herds, most (if not nearly all) outcomes are known by 42-63 days past the end of a given interval. A survey of current Minnesota DHIA indicates that 95% (or even 97%) known outcomes is readily achievable by many herds. Cows that can not be included as "eligible" would be cows that received inseminations without a subsequent preg/open diagnosis and that also did not receive another later insemination. These are mainly either cows that were sold/died soon afterwards or cows not yet con firmed pregnant or open. The unconfirmed cows can be included once the outcomes are known. Therefore, reporting outcomes of breedings promptly and completely will improve the accuracy of the calculation. Pregnancy rate can be calculated regardless of whet her AI, bulls, or a combination are used. Note there is no need to know conception rate nor heat detection rate to calculate pregnancy rate.

Pregnancy Rates are part of the 21day heat trial BREDSUM option. Its columns are:

• Date     Start date of each 21-day interval.
• Ht Elig  Number of cows entering the interval eligible to be detected in heat. Default is eligible for heat at 50 DIM (VWP=50).
• Heat     Number of cows actually detected in heat or inseminated.
• Pct       Number of cows actually detected in heat/Total eligible (shown as Percentage).
• Pg Elig  Number of cows entering interval eligible to become pregnant. If number is smaller than the Ht Elig number, it means there are unknown outcomes of some of the breedings.
• Preg     Number of pregnancies.
• Pct       Number of Pregnancies/Total eligible to become pregnant (shown as Percentage).
• Abort    Count of breedings that resulted in a pregnancy, but were later lost.

By default only cows in AI pens are considered in the BREDSUM\E option. Once a cow enters a bullpen, she is no longer included in the heat detection measurement beyond her bullpen entry date. Conceptions that occurred prior to bullpen entry are included, but no conceptions that occurred after bullpen entry are counted. Please see bullpen documentation for proper on-farm bullpen setup.

Additionally, if a cow is designated as a Do Not Breed, she will not be considered in the calculations for dates after being marked as DNB. At the bottom of the report the total for the year (or other time interval if \D is used) is reported. The heat detection rate is calculated through yesterday. (Note that the heat detection rate for a given interval may drop in the future as cows diagnosed open will then have a "missed" heat retroactively inserted at the appropriate times.) The pregnancy rate is c urrent to 42 days ago.

The pregnancy rate (Pct preg) in this example herd is 14% for the year. Notice that the pregnancy rate has ranged from 4% to 18% for any individual 21-day interval over the past year. The rate for each 21-day period is calculated by dividing the number Preg by Pg Elig for that period. The Total rate is calculated by dividing the Total Preg by the Total Pg Elig. This herd has a 66% heat detection rate over the year. The heat detection rate has ranged from 51% to 83% du ring any individual 21-day periods over the past year. The criteria to be eligible to be in heat (inseminated) is the same as the criteria for being eligible to become pregnant. Typically, there are a few more heat eligible cows due to cows that are insem inated, but remain an unknown outcome (either conception status not entered or the cow was sold prior to determining the outcome of the insemination).

To bring up a list of the cows included in the calculations just click on the date for the period you want displayed. In this example cow # 1121 is one of the cows that was bred during the period starting on 3/12/04, became pregnant to that breeding, but later aborted.

Here is an example using the same herd, but running the report as BREDSUM\ED and choosing 1/1/04 as the starting date. Note that the Pregnancy Rate (Pct) for this time frame is 16% as compared to 14% for the 378 days of the default report, and reflect an improvement in recent months.