Determine Conception at 21-Day Intervals:
The Table shows how to use BioPRYN® in a bull breeding program with 100 cows. The breeding period, beginning with Day 0 when bulls are introduced into the herd, is divided into five 21-day cycles, the last ending with 105 days (see line 1).

An assumption was made that conception rate is 50% and that the bulls detect 100% of the heats. The predicted number that become pregnant during each of the five cycles is shown in line 2 and in the shaded bars (lines 3A through 3D).

Lines 3A through 3D show four different days after bull introduction that the blood sample is collected for the BioPRYN® test for pregnancy. These days of collection allow detection of conception during any of the 21-day cycles. Sampling all cows at Day 51 will detect any conception during the first 21 days of breeding. BioPRYN® can detect early at 30 days of embryo age; the cows conceiving after day 21 will not be 30 days old and will not be detected. Those detected open on Day 51 are tested again at Day 72 to find those conceiving during the 2nd cycle. Continue this progression across the table.

Eliminate Late Calvers/Select Length of Calving Season:
The number pregnant or open at the end of each cycle is shown across the bottom of the table. Again, it is assumed a 50% conception rate and 100% heat detection. At the end of 3 cycles, 88 of 100 cows are pregnant and 12 are open. Testing once at 93 days would identify all these animals; testing on all days on lines 3A - 3D is optional. A decision to cull those open at this time will provide a calving season near 63 days in length.

Selection of any length of calving season is possible by using BioPRYN® testing. For example, if one wanted an approximate 45 day calving season, collect a BioPRYN® sample 75 days after introductions of bulls. This is 45 days of breeding plus the 30 days until the last ones conceiving on Day 45 can be tested with BioPRYN®. Cull the open cows.

Determine AI Conception with Back-Up Bull Breeding:
If an AI program is used along with ovulation and estrus synchronization, it is easy to apply BioPRYN® to all cows 30 days after the synchronized AI. Do not place bulls with the herd until 16 days after AI if follow-up bull breeding is desired. Since the cycle had been synchronized, only rare cycles will begin in non-conceiving cows before this time. Testing at 30 to 35 days will not detect back-up bull breeding but will detect AI breeding. Continue BioPRYN® testing in the herd with the timing as above and with the 16th day becoming day 0 (time of introduction of bulls). See the Breeding Calculator on the BioTracking LLC web site to calculate calendar dates for this AI and bull breeding program.