An estimated 75 percent of North Dakota dairy producers use artificial insemination (AI) for impregnating heifers.

""Artificial insemination provides genetic advancement within the herd, such as conformation and milk production; ensures monitoring of semen quality and fertility of AI bulls; eliminates the spread of veneral disease; provides farmers with information on calving ease to reduce problems with dystocia; provides a merchandising advantage for AI-sired heifers; and offers better control of the time when heifers calve,” says J.W. Schroeder, North Dakota State University Extension Service dairy specialist.

He adds that the major reasons for not using AI for heifers is the perception of lowered conception rate for AI, a time commitment for heat detection, the need to keep heifers at an inconvenient location and the lack of restraint facilities.

If problems associated with daily estrous detection limit the use of AI, then dairy producers should give serious consideration to using a synchronization program, Schroeder says. A variety of systems are available, one of which should suit a specific herd situation.

To achieve success with a synchronization and AI program, a producer must commit to following the procedures carefully and paying attention to detail, he says. Producers also should note the heifers that fail to conceive after the initial insemination will tend to return to estrus in a synchronized pattern.

Most dairy heifers are bred based on observation of spontaneous heat, and the conception rate usually ranges from 50 percent to 76 percent. Other protocols used in heifers include prostaglandin (PG), intravaginal progesterone inserts (CIDR) and timed artificial insemination (TAI). Recent research conducted at the University of Idaho investigated these protocols on an Idaho dairy.

For that research, 13-month-old Holstein heifers were assigned to one the following:

• Control (daily tail paint, AI on detection of spontaneous heat)
• PG (one PG injection at enrollment, AI on detected heat; those not bred received a second PG injection after 14 days and AI on detected heat)
• CIDR (CIDR insert for seven days, PG injection at CIDR removal, AI on detected heat during three days after CIDR removal; heifers not inseminated by 72 hours after CIDR removal received TAI and gonadotropin-releasing hormone, or GnRH, injection)
• TAI (GnRH injection, six days later insertion of CIDR and injections of PG and GnRH, seven days later CIDR removal and PG injection, and TAI with GnRH injection 48 hours after CIDR removal).

The TAI protocol extended the interval from enrollment to AI and conception by about five days, produced the fewest pregnant heifers (46.9 percent conception rate) at the end of the 28-day breeding program and had the highest cost per pregnancy ($84.89). Heifers in the PG group had the highest conception rate (62.8 percent). Control and PG groups had the lowest breeding program cost and cost per pregnancy (control $42.01 and PG $40.02).

“The take-home message for dairy managers is when heat detection is effective, simple protocols based on detection of spontaneous or PG-induced heat can economically provide high reproductive efficiency,” Schroeder says. “If heat detection is not adequate, these protocols are less likely to be successful. As more information becomes available about the mechanisms controlling follicular development, more precise synchronization programs will be developed, but good results are being obtained with currently available systems.”

NDSU Agriculture Communication