Several factors must be considered when deciding what AI synchronization program to use in your herd. One of the first is whether you have the time to heat detect yourself or if you want timed breeding.
Cost is a consideration, as timed AI programs require more financial commitment and more passes through the chute.
The three main synchronization programs I find most successful are among several options now available. Your veterinarian or semen sales rep may recommend programs as well. Drugs required for these synchronization programs are available through prescription.
Also talk to neighbours to see which programs they’ve had success with. The key is not to get them too complicated. Write down the protocol to follow so nothing is left to chance. Success depends on undertaking all the details.
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 apply to AI and must be incorporated into a synchronization program.
Synchronization is not a substitute for poor management. Heifers must be at the two-thirds mature weight in order to breed. Adequate energy and trace minerals must be in the ration. A good body condition score of between 2.5 to 3.5 is necessary. Have the cattle vaccinated for the reproductive diseases that may be 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 program.
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 shots are given 10 days apart and cattle are observed very closely for heats two to five days after the second shot, then bred accordingly.
Be very careful as the two commonly used prostaglandins on the market have a different dosage. Lutalyse, the natural one, is five cc and estrumate, the synthetic one, is 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. The neck muscles are preferred for all these injected products.
As a slight variation, producer can observe and breed off heats picked up after the first shot of prostaglandin. If cycling well previously, approximately 70 per cent of the cows will cycle in the first several days after the first shot. Those 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.
Program for heifers only
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 MGA at a rate of 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 then stopped. Since the progesterone source is removed, almost all of the heifers will come into heat within two to six days. A big word of caution — this is NOT a fertile heat.
To achieve that, we then go in with a prostaglandin shot (remember the dosage difference) 17 days after the removal of the MGA. The heifers will be in standing heat within two to five days after the injection and are then bred according to heat. This program does not work on cows even when a higher dosage of MGA was used. Do not under any circumstances use this program on cows. The results are much too inconsistent.
Advantages of the MGA heifer program include reduced cost and only two passes through the chute, including one pass to AI them. With any of these programs, natural breeding could also be used, but bull power is critical as many more animals are cycling over a short period. Natural breeding will work with fertile bulls in small breeding groups.
If you do the math, the MGA program 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.
For heifers and cows
The last program involves the use of controlled internal drug release (CIDR) and fixed time AI — all cattle on the program are bred at a specific time. Both labour and management are put to efficient use. If hiring a technician, the whole group is AIed together.
The CIDR is a vaginal implant, which releases a controlled amount of progesterone dAIly. There are probably 15 different programs using CIDR in the industry today. One easy-to-follow program I’ve found to provide the best results includes:
- Step 1, day zero — the cattle are run through the chute and the CIDR placed in the vagina. They are also given a shot of one of the gonadotropin-releasing hormone (GNRH) products that are on the market. This product will get a follicular wave, started allowing the CIDRs will induce cyclicity on those cows. Tuck the tail neatly inside the vulval lips.
- Step 2, day seven — the CIDRs are removed and a prostaglandin is given at the regular dosage.
- Step 3 — The animals are given a second shot of GNRH when AIed, which is right on 52 to 56 hours after the prostaglandin shot with heifers and 60 to 66 hours with cows. The heifers respond essentially 10 hours quicker and that is why the shorter breeding time. The real advantage of this program is the timed AI. However it’s more expensive and the cattle are run through the chute a total of three times, including the one to inseminate them.
All three programs have merit, but discuss with your veterinarian which one he/she would recommend for your circumstance. The goal is to get as high a conception rate as possible in a short period.
Conception rates with all these programs depend on attention to detail, but should be very close to those achieved by breeding off natural heat cycles.