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A.I. & Breeding

From estrus and heat detection to genomics and sexed semen, discover the latest information to improve reproductive performance.


The doubling of milk production per cow in the U.S. in the last 50 years did not happen by chance. Research data since the use of A.I. in dairy herds enrolled in the Dairy Herd Improvement (DHI) program clearly shows that selection for genetic merit for milk yield and the positive environment for feeding and husbandry are about equally responsible for this improvement in milk production.

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World Wide Sires 2009
With the release of the April 2009 genetic evaluations, World Wide Sires adds 15 new Holstein bulls to our line-up, sired by 10 different sire fathers.

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Achieving a high, accurate heat-detection rate (HDR) is a major challenge to dairy producers. There are management issues affecting HDR such as labor constraints, commitment to effective heat detection and inaccurate submission of cows for insemination. Furthermore there is good evidence that cow factors and environmental conditions significantly contribute to a reduction in the expression of estrus.

When herd managers cannot maintain an effective visual heat detection program, they have several options to improve submission rates for breeding. These include implementing an estrous synchronization/timed insemination program, routine use of heat detection aids, contracting heat detection to artificial insemination personnel or resorting to use of natural service.

A survey of 103 large herds with an average herd size of 613 cows across the U.S. revealed that approximately 90 percent of the herds used synchronization/timed A.I. programs and a majority also used heat detection aids. A recent report from USDA documented that the average days to first service in the U.S. has decreased six days between 2001 and 2005. This may be indirect evidence that timed A.I. programs are improving submission rates to insemination. Furthermore, research published in the Journal of Dairy Science reported that herds using synchronization programs have 17 fewer days open.

Data presented at the Dairy Cattle Reproduction Council annual conference provided data from a direct comparison of a timed A.I. (TAI) program with natural service (NS) in a large herd. Beginning at 42±3 days cows in the TAI group were assigned to a Presynch – Ovsynch 56 program. Eighteen days following insemination a CIDR was inserted and GnRH was injected seven days later (25 days after original TAI).

Cows diagnosed not pregnant by ultrasound at 32 days were administered prostaglandin (PG), followed by GnRH at 56 hours and inseminated 16 hours later (resynchronization). Pregnant cows were reexamined by rectal palpation at 60 days.

Cows in the NS group received PG at 42±3 and 56±3 days and moved to pens with bulls at 70 days. The bull- to-cow ratio was 1 to 20 and bulls were rested for 14 days after a 14-day exposure to cows. Bulls also received a breeding soundness examination. Ultrasound at 42 days was used to determine pregnancy status in this group.

Preliminary results during the cooler months in Florida (December 2006 to May 2007) are as follows. The median time when 50 percent of the cows were pregnant in either group was 104 and 103 days for TAI and NS, respectively. There was no significant difference between groups.

However, there was a significant difference in pregnancy rate for first service through 91 days postpartum, as 25 percent of all pregnant cows conceived 11 days earlier in the TAI group. Pregnancy losses estimated over four services were 14.9 percent and 11.8 percent for TAI and NS groups, respectively.

The researchers noted that when compared to the NS group, more cows in the TAI group were submitted for insemination during a narrow window of time. Furthermore, the pregnancy rates of 45.9 percent to first service and 32.7 percent to resynchronization at second service indicate a very good response to TAI.

In summary, this is another controlled study showing no significant advantage to NS. When the direct and indirect expenses of NS are considered, there is a cost and risk associated with NS. It is the responsibility of the dairy producer to provide a safe working environment for employees and family. PD

References omitted but are available upon request at

—Excerpts from Penn State Dairy Digest, October 2008

Michael O’Connor
Dairy Extension
Penn State

Synchronization and artificial insemination (A.I.) are effective tools to build a better herd. However they are only as effective as the planning and implementation put into both of those programs.

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In the old days, we expected to get a 50 to 55 percent conception rate (1.9 to 2 services per conception) with milking cows. We have done a great job of breeding high-producing Holsteins. Unfortunately, the modern high-producing Holstein is not highly fertile, and the conception rate in many high-producing herds is 40 percent (2.5 services per conception) or lower.

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A healthy calving program is an integral part of a strong dairy business. Especially now that milk prices are low, losing calves or missing conceptions will take a toll on your bottom line. Dyecrest Dairy on the Front Range of Colorado has had great success in keeping their registered herd full of replacements. Dairy owner Terry Dye has entrusted the A.I. and calving aspect of the dairy to his daughter, Amanda Dye, for the past 20 years.

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