Producers who think their heifer reproduction programs are on track may want to look again. Conception rate and percentage of heifers pregnant within three services are metrics commonly used to track performance of heifer reproduction. Unfortunately, time is the missing component from both of these heifer reproductive measurements.

“Conception rate and percentage of heifers pregnant within three services keep enough heifers in the calving pipeline to maintain herd size. However, neither accounts for how long it takes for a heifer to join the milking string,” explains John Lee, DVM, Veterinary Operations, Pfizer Animal Health. “The gold standard for monitoring reproduction in heifers, just as in cows, is how quickly open heifers are converted to pregnant heifers or pregnancy rate. Determining which management aspects will have the greatest affect on pregnancy rate will drive the reproductive success of all heifers.” 

Lee says getting heifers inseminated soon after the end of the voluntary waiting period will have an enormous impact on pregnancy rate because the likelihood of conception to that first service is high. Heifers have higher fertility than lactating cows, so even a few small steps to improve their performance will pay off rather quickly. The Pfizer veterinarian recommends the following five steps that should significantly improve the management of first service breeding in heifers.

Step 1: Move heifers to the breeding pen.

Heifers should be moved into the artificial insemination (AI) pen as they reach height and weight targets and are ready for breeding. On most dairies, heifers should be moved at least every two weeks but weekly is better. Pen management is the biggest opportunity for improvement on most operations. 


Step 2: Use prostaglandin on date of move.

Administer prostaglandin on the day of movement and again 10 to 12 days later for heifers not yet inseminated.


Step 3: Make sure all heifers are inseminated.

Consider using a progesterone-releasing insert (CIDR) for timed breeding on heifers not inseminated during their first 28 days in the breeding pen. This will ensure all heifers are inseminated within 36 days of arrival into the AI pen.


Step 4: Routine pregnancy checks.

Pregnancy diagnosis must be conducted routinely as heifers are moved to the breeding pen to identify pregnant females and move them out, making room for new heifers. All pregnancies should be reconfirmed at 70 to 90 days carried calf.


Step 5: Re-enroll open heifers.

At each pregnancy check, any heifers that aren’t bred should be immediately submitted to a breeding program with prostaglandin and/or a CIDR.


“There is a sizable financial advantage for a heifer that calves for the first time at 23 months of age versus one that freshens at 25 or 26 months of age,” Lee says. “The incremental costs are minimal compared with the benefits of heifers spending less time in the bred heifer pen, and more time in the milking string.”


Source: Pfizer Animal Health