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Virginia Cooperative Extension -
 Knowledge for the CommonWealth

The Cow-Calf Manager

Livestock Update, October 2006

John B. Hall, Extension Animal Scientist, Beef, Virginia Tech, and Dee Whittier, DVM, Extension Veterinarian.

Cows Can Now Be Successfully Bred By AI on A Single Day

Artificial insemination of cows in commercial herds has been slow to catch on for a variety of reasons, but recent changes in estrous synchronization systems as well as the move towards value-based marketing makes AI in commercial herds a strategy to consider.  Over the years, estrous synchronization systems improved, but producers still had to check heat twice a day for at least 3 to 5 days as well as breed cows at 12 hours after they came in heat.  That was still a considerable amount of labor.  In addition, it was hard for producers with small herds to find technicians to breed a few cows a day.

Recent estrous synchronization research has focused on systems to AI cattle on a single day without checking heat.  These systems are called Fixed Time AI systems or FTAI.  The CO-Synch+CIDR system (Figure 1.) was developed at Colorado State University and has been tested by universities across the US.  Results with this system are good with 50% to 65% of the cows becoming pregnant to a single AI breeding on one day.

GnRH = Cystorelin®, Factrel®, Fertagyl®, OvaCyst®

PG = Lutalyse®, Prostamate®, In-Synch®, estroPLAN®, Estrumate®

Results with CO-Synch+CIDR in Virginia
Over the past two years, we conducted research on CO-Synch+CIDR in Virginia herds of various sizes.  The research was completed in collaboration with Dr. Ramanathan Kasimanickam from the VA-MD College of Veterinary Medicine, the VA Department of Corrections, Extension Agents, and cooperating beef producers.  Over 1400 cows were bred on 10 farms with an average pregnancy rate of 56.3% (Figure 2). The range in pregnancy rates was between 51% and 76% with most of the herds around 55%.

It’s not just the synchronization system
Other management procedures have to be done correctly for cows to breed well to AI.  All the herds in studies reported above had calving seasons of 90 days or less.  All cows were from well vaccinated herds.  In addition, the managers had paid careful attention to nutrition so most of the cows were in body condition score 5 to 6.  Still thin cows and cows that had calved less than 60 days before breeding has lower pregnancy rates compared to fleshier, early calving cows (Table 1 & 2).  Producers need to make sure they have good management in place before investing in an estrous synchronization and AI program.

Table 1. Impact of body condition score at breed on pregnancy rate to fixed time AI and overall pregnancy rate

Body condition score
Pregnant to FTAI
Pregnant to AI plus Clean-up bull
4 or less 46.4% (78/168)a 82.7% (139/168)a
5 to 6 56.0% (566/1011)b 89.3% (903/1011)b
7 or greater 64.4% (172/267)c 92.9% (248/267)c

a,b,c Averages within column with different superscripts are different (P < 0.05).
Adapted from Kasimanickam et al., 2006

Table 2. Effect of days postpartum on pregnancy rates to fixed time AI.

Days since calving at start of the breeding season
Pregnant to FTAI
60 or less 49.2 %  (186/378)a
61 to 80 60.8% (400/658)b
81 or greater 56.1% (230/410)b

a,b Averages within column with different superscripts are different (P < 0.05).
Adapted from Kasimanickam et al., 2006

Surprisingly, young cows (2 year-olds) had pregnancy rates similar to mature cows with cows of all ages averaging about 56% pregnant to fixed time AI.

Many producers are concerned about cows bred on the same day calving on a single day. Research from Missouri and other locations proved that calves from cows bred on the same day will be born over a two week period.  This is due to the natural variation in gestation length.  In a herd of 60 cows that translates into 4 to 6 calves being born on the busiest day.  Most days only 2 or 3 calves will be born.

If you have more questions about AI and estrous synchronization systems, contact Dr. John Hall, your AI representative or your Animal Science Extension Agent.

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