Artificial insemination (AI) has many advantages relative to increasing the genetic quality of your herd. However, achieving acceptable pregnancy rates with AI requires excellent heat detection skills and labor. Heat detection requires approximately 3 hours per day for at least 21 days. The part-time producer is hard pressed to justify the additional labor requirements even for better genetics. With the advent of estrous synchronization (ES) protocols that are easy to use and produce acceptable rates of pregnancy, the labor involved in checking heat has been greatly reduced. This has opened up a huge opportunity for farms with herds of all sizes, but especially smaller herds, to take advantage of the benefits of AI.

Although cattle were being artificially inseminated on a commercial scale by the late 1930s, the first documented case (1322 A.D.) goes back to an Arabian chieftain who inseminated his mare to an enemy’s stallion. The dairy industry was quick to adopt AI, but due to the extensive nature of beef management the labor involved in detecting heat prevented widespread use in beef herds. In 1935 researchers discovered lipid extracts that caused contractions of the uterus and would eventually be named progesterone and prostaglandin; the primary hormones used in estrous synchronization. In the mid-1960s research ramped up to find an ES program that was practical and cost effective. A better understanding of reproductive biology in the 1980s finally led to the basis of the ES protocols that are in place today.

Synchronization of estrous is accomplished by manipulating the reproductive cycle such that a high percentage of females come into heat in a short, predefined time span. Tim Dennis, DVM, reminded attendees at the New York Beef Producer’s Winter Management meeting in Syracuse that estrous synchronization is really ovulation synchrony. Therefore you might not observe much estrus activity. There are many ES protocols that can be sorted into three categories: (1) Heat detection or not, (2) Low versus higher cost, (3) Some labor versus more labor. The scope of this article does not allow for discussion of all of the protocols. You should work with your veterinarian and AI technician to determine the best protocol for your situation.

It’s important to understand that if you plan to minimize labor and keep a calving interval of less than 90 days, ES and AI will not replace the natural service bull. However, these technologies will reduce the number of bulls required. For example when implemented correctly, ES followed by AI should result in a 65 percent conception rate to AI. Using the recommended ratio of one bull per 25 females, a 50-cow herd would require two bulls; however, if 65 percent were pregnant to AI, that would leave only 18 cows to be covered. This herd could conceivably go from two bulls down to one bull. Given that the average cost of a quality bull is $4,000 to $5,000, this is a significant savings.

Consider Benefits to Using ES

1. Performance.

a. Synchronization results in more calves being born early in the calving season. These calves are older and heavier at weaning.

b. Cows that calve early have more time to return to estrous, will breed back sooner and therefore keep calving early.

c. Research from Nebraska shows that calves born in the first 20 days of the calving season continue to outperform their later born contemporaries all the way through to slaughter.

2. Economics.

a. Older, heavier calves produce greater gross receipts per head than younger, lighter calves.

b. Early born calves have greater carcass weight, higher marbling scores and greater percent USDA Choice.

c. Allows for an increase in herd size without an increase in the number of natural service bulls.

3. Convenience. For the part-time farmer, this may be the greatest incentive.

a. Choose a time frame to breed cows that is convenient to your schedule and labor availability as compared to checking heat two to three times per day for 21 days.

b. Some AI companies will only breed a minimum number of cows. Having all cows bred in a short time may make it easier to obtain services of a breeder.

c. If I know that at least 65 percent of my cows will calve within a five- to 10-day window, I can focus my efforts such that I’m not out of town and available to check the cows on a more regular schedule.

d. If I’ve correctly chosen the bull, calving ease will be increased, and I won’t have given up any growth. Using a natural service sire, my options for these “spread” bulls will be more limited.

(Modified from Pruitt, 1994.) Source: Virginia Cooperative Extensnion 

Challenges to ES and AI:

Body condition score. On a scale from 1-9 (see table 1), cows that are not at least 5 and heifers 5 to 6 may not respond adequately to cover labor and cost.

Facilities. A system that is low stress to capture females and restrain them is essential.

Labor and expense. Not as easy as opening the gate and letting the bull out. Expenses are associated with semen, breeding fee, hormones and supplies.

Management. Calving multiple cows in a short time can cause stress on manager and facilities.

Weather. Pregnancy rates can be affected by extremely hot weather.

Freak weather events. Not common, but a blizzard that hits during a synchronized calving can be a real disaster.

Strict adherence to protocols is absolutely required to get cows pregnant!

The data in Table 2 was gathered over three years on a part-time commercial beef herd in New York. All cows were synchronized and time bred with some heat detection. For cows, a CIDR (controlled internal drug release, an intravaginal progesterone insert) was inserted on day 0 and given GnRH. Seven days later the CIDR was removed and prostaglandin was administered. Through 60 to 66 hours any cow showing heat was bred. Any that did not come in heat by 66 hours were given GnRH and bred. The heifer protocol was the same, other than that the time between removal of the CIDR and breeding was reduced to 54 hours.

The heifers were bred in June and cows in July. The overall pregnancy rate was excellent. While body condition score was not recorded, given its importance in reproduction, it would be a pretty good guess that the cows were in good condition. Pregnancy rates to AI varied from 47 percent to 75 percent with an average of 61 percent for the cows and 60 percent for the heifers. This was accomplished by running the herd through the chute two times, detection of heat over a 36-hour period and breeding most of the cows on time (66 hours or 54 hours for cows and heifers, respectively).

Increased weight at weaning is also evident in this herd. On average calves out of cows bred AI were 68 pounds heavier and out of heifers were 79 pounds heavier compared to calves out of natural service sires. Most of this was due to the AI calves being older, but a portion can be attributed to increased growth genetics of superior AI bulls.

Cost for CIDR and hormones is just under $15 per herd. Breeding service is $8 per herd and semen $15 to $25 per herd. Therefore you have about $45 per herd in ES and AI cost. You still need to include the cost of a natural service bull; however, as stated previously, you can spread his cost over more cows.

We’re in a pretty good place with beef prices.

Cover Photo: Batman2000/istock