Getting Cows Bred in a Fixed Time Program by: Barry Potter, Agriculture Development Advisor, OMAFRA

As a summer student at (what was) the New Liskeard College of Agriculture Technology (NLCAT), I was hired to work on a research program that looked at synchronizing cows so they would all calve within a tight time frame. I was told to expect to be very busy right from the get-go, as my first day of work was the start of the expected calving date. Unfortunately, or fortunately for a green, wide-eyed university student, pregnancy results of the synchronizing program, using a product called Synchromate B, were very low, resulting in a slow, uneventful calving season. Undeterred, the research has continued, trying different programs and methods for synchronizing the beef cows from the NLCAT to today’s New Liskeard Agriculture Research Station (NLARS).

That summer we tried a method where we removed the calves from the cows for 48 hours, hoping to stimulate reproductive hormones. What I remember is we stimulated a lot of cranky cows.
The game changer for synchronizing cows at NLARS occurred in the mid 1990’s with the advent of the use of the CIDR-Ovsynch program. This program involves inserting a progesterone drenched plastic T into the cow’s vagina and using other hormone therapies to program the cows for synchronized breeding. NLARS is one of the research stations associated with the University of Guelph. Working closely with Guelph reproductive researchers, NLARS has fine-tuned the process, providing the industry with a standard process for using artificial insemination effectively on the farm, and synchronizing cows so calving occurs within a close timeframe. Currently cows and heifers are synchronized using hormone therapy and breeding them on day eight from the start of the synchronization.

The products used in the process include:

• CIDR: Controlled Internal Drug Release device
• GnRH: Gonadotropin Releasing Hormone
• PG: Prostaglandin

Figure 1. CIDR (Controlled Internal Drug Release Device) and applicator

These products can be used strategically to manipulate the estrous cycle of the cows in the herd so that all cows can be inseminated at the same time. This allows for labour saving and effective use of resources required for artificial insemination. The cows will also calve in a tighter calving group, resulting in labour and efficiencies at calving time as well.

Figure 1. Fixed Time Insemination Protocol (First A.I.)

Figure 2. Fixed Time Insemination Protocol (Second A.I.)

*Product Trade Name examples provided by Beef Reproductive Task Force 2016

The cows and heifers are programmed at the same time and bred all at the same fixed time.

At day 28 from the insemination date, the breeding females are reprogrammed with CIDRs, and given GnRH. At day 33 from insemination, the CIDRs are pulled, and the females are ultra-sounded for pregnancy. Any female that is not detected as pregnant is given prostaglandin. The non-pregnant females get a second prostaglandin the next day. On day 36 from the first insemination they are artificially bred again.

This process, while very labour intensive over short periods of time, has proven very effective in getting animals pregnant.

Table 1: NLARS Pregnancy Rates from Fixed Time Insemination

When you consider that a good bull will impregnate around 70% of the cows he breeds the first time around, the results for the first fixed time insemination is about as good. By following up with the second fixed time A.I., 91% of the breeding females are bred within a 36-day breeding period.

Cost Comparison

Table 2 provides the costs for the programming and breeding of cows artificially. These prices were worked on a basis of 100 cows, and then converted back to a cost per cow, based on pregnancy rates, and usages each time.

CIDRs are reused for the second synch. Only one pregnancy check cost was inputted. While two are required, it is assumed that a regular bull bred herd would also incur the cost of one pregnancy check. No semen costs were inputted. An assumption was made that the cost for a bull to service a cow would be the same as a straw of semen.

Table 2. Cost of artificial insemination using the CIDR-Ovsynch program

¹ Priced based on %, using 100 cows
² GNRH given to all cows 2 X first time and 1.3 X the second time based on 70 % pregnancy first insemination
³ Prostaglandin given to all cows 2 X 1st Synch, and 2 X 30 % at 2nd Synch
⁴ 5 cow handlings at 4 minutes each per cow

The total cost for breeding a cow through artificial insemination in this example is $72.54.

Cost of a bull

How does this compare to having a bull around? Accounting for the approximate feed and health costs for caring for a bull, the cost of getting a cow pregnant by a bull is estimated to be $52.50 (Table 3).

Table 3. Bull costs per cow

Costs include feed and health, plus yearly semen test
*Assumes 30 services per bull

While on paper a bull may appear $20 per pregnancy cheaper, there are many advantages to this detailed artificial insemination protocol not captured in this price comparison. These advantages include:

• Shorter breeding period and tighter calving groups. Having a tight calving group provides more marketable calves.
• A.I. allows for targeted mating of cows and heifers. One can select calving ease bulls for heifers, perhaps carcass trait bulls for older cows, etc.
• The fixed time A.I. program reduces labour, making use of this technology more practical.
• Eliminating walking bulls can eliminate bigger, more aggressive animals, reducing safety concerns around the livestock. Bulls also tend to do a lot of damage to facilities and fences just by rubbing on them.

Each farm needs to evaluate whether and how artificial insemination can work on their farm. Research over many years at the New Liskeard Agriculture Research Station shows that it can be effective.