Several factors must be considered when deciding what synchronization program to use in your cattle herd.
Do you have the time to heat detect or do you want timed breeding? Cost is a consideration, as timed artificial insemination programs require more financial commitment and more passes through the chute.
We will explore three main synchronization programs that I personally find the most successful. There are numerous options available now, and your veterinarian or semen sales rep may have programs they recommend. Also, talk to neighbours to see which programs they have had success with.
The key is to have one that is not too complicated, and to write the protocol down so nothing is left to chance. Success depends on dealing with all the details and following the protocols as closely as possible.
With any synchronization program, cows and heifers must be in good health and have a sound nutritional program. All the factors that lead to a high conception rate with natural breeding are the same ones that must be incorporated into a synchronization program.
Synchronization is not a substitute for poor management.
Heifers must be at two-thirds of mature weight in order to breed. Adequate energy and trace minerals must be in the ration. A good body condition score of 2.5-3.5 is necessary. Have the cattle vaccinated for the reproductive diseases that are in your area (such as BVD and IBR). Recently calved cows should be gaining weight on a rising plane of nutrition and be at least 60 days postpartum. If the semen is of high quality, the only thing left is to fine-tune the synchronization programs, so please read on.
If labour is not an issue and the skill level for heat detection is high, the original program of two shots of prostaglandin is still very effective. The two shots are given 10 days apart and cattle are observed very closely for heats for two to five days after the second shot, and then bred accordingly.
Most prostaglandins, including the commonly used one estrumate, have a two-cc dosage. Always, always, give these products with a long needle (at least 1.5 inches) as you must get this low-dosage product deep into the muscle. It is preferable to use the neck muscles for all these injected products.
The only other slight variation to this program I use is when a producer wants to observe and breed off heats picked up after the first shot of prostaglandin. If they are cycling well previously, approximately 70 per cent of the cows will cycle in the first several days after the first shot. Any that aren’t bred after the 10 days are then given the second shot.
This cuts your cost but increases labour as you are breeding over a longer period of time.
An excellent program — but only for heifers — is the MGA (megesterol acetate) program. MGA is a progesterone compound, which was primarily used in feedlots to keep heifers from cycling. Heifers are fed 0.5 mg/hd/day for 14 days (most feed mills will have this mixed in a small amount of grain or in pellet form, making it easy to administer the proper amount). This is fed for 14 days exactly and then stopped. Since the progesterone source is removed, almost all of the heifers will come into heat in two to six days.
A big word of caution here is this is NOT a fertile heat. We then go in with a prostaglandin shot (remember the dosage difference), 19 days after the removal of the MGA. The heifers will be in standing heat two to five days after the injection and are then bred according to heat or are all AI’ed in 72 hours. This program does not work on cows even when a higher dosage of MGA was used, so do not under any circumstances use this program on cows. The results are way too inconsistent.
The advantage of the MGA program is that the cost is reduced and only two passes through the chute are required (when we count the one pass to AI them).
With any of these programs one could use natural breeding, but bull power is critical as many more animals are cycling over a short period of time. Natural breeding will work with fertile bulls in small breeding groups. The MGA program (if you do the math) needs to be started 33 days (just over one month) before you wish to breed the first heifer. Some larger producers will synchronize their heifers in two groups to avoid a large number of heifers calving very close together.
The last program involves the use of CIDR (controlled internal drug release) and fixed-timed AI (where all cattle on the program are bred at a specific time). The advantage is that labour and management are put to efficient use. If hiring a technician, the whole group is AI’ed together.
CIDR is a vaginal implant, which releases a controlled amount of progesterone daily. There are probably 15 different programs using CIDR out in the industry today. I will outline one that I feel gives good results and is the easiest to follow.
On Day 0, the cattle are run through the chute and the CIDR placed in the vagina and they are given a shot of GnRH. There are several brand names of GnRH on the market including, but not limited to, Fertagyl, Cystorelin, and Fertilene. These GnRH products will get a follicular wave started and the CIDRs will induce cyclicity on those cows.
The string tail is often clipped off when used on heifers so they aren’t pulled out. Tuck the tail neatly inside the vulval lips. On Day 7, the CIDRs are removed and a prostaglandin is given at the regular dosage. The animals are given a second shot of GnRH at the time of AI (which is for heifers 54 hours plus or minus two hours). This means you don’t synchronize more than you can comfortably AI in two to three hours.
The real advantage of this program is the timed AI. The sacrifices are it is a more expensive program and the cattle are run through the chute a total of three times, including the one to inseminate them. Some will separately AI those heifers, which cycle real early or re-AI’ing those which come in standing heat after the timed AI. Although a bit more work, this will help to boost conception rates.
All three programs have merit. Ask your veterinarian which one he/she would recommend for your circumstances. The goal is getting as high a conception rate as possible in as short a period of time.
Conception rates with all these programs depend on attention to detail but should be very close to those achieved by breeding off of natural heats. We often say 50 per cent to be conservative but others approach 70 per cent.
Hopefully breeding season goes well and if contemplating synchronization, discuss it with your herd veterinarian.