Being in the midst of calving, it is hard to think about next year’s calf crop. However, with the 2020 AI beef sire directories available, it is time to think about breeding season especially if you will be using synchronization. Depending on which protocol is selected, it could be over 35 days from start of the program to artificial insemination. This means, if you begin breeding May 15 for a February 20 calving date, you will need to start synchronizing heifers April 12 if using the 14-day CIDR + PG protocol. As a result, the need to purchase CIDRs or MGA need to be on the top of the “to do” list.
The Beef Reproduction Task Force, composed of AI and pharmaceutical company representatives, veterinarians and university reproductive specialist have developed a list of synchronization protocols recommended for heifers, based on research data and field use. The recommended protocols can be found in genetic company catalogs and the Beef Reproduction Task Force website. To help compare synchronization protocols, and to develop synchronization and breeding calendars consider using the free Estrus Synchronization Planner.
Heifer Estrous Synchronization Protocols
The recommended heifer estrous synchronization protocols have been put into one of three categories: 1) Heat Detection Protocol; 2) Heat Detection and Timed AI Protocol and 3) Fixed Time AI Protocol.
Heat Detection Protocols
Heifers in these protocols should be inseminated 12 hours after the first observation of standing heat. Peak heat activity occurs approximately 48 to 72 hours after prostaglandin. In order to optimize AI pregnancy rates, heat detection should occur at minimum 3 times per day for at least 1 hour per check. This equates to a total of 3 hours per day heat checking with 5 to 6 hours of heat check increasing overall AI pregnancy rates. It is also important to train individuals to detect signs of heat (Table 1) and application of a heat detection aid will help assist in determining heifers in heat when no one is watching. The heat detection protocols for heifers include:
- 1 Shot PG (Prostaglandin)
- 7-day CIDR®-PG
|Before Standing Heat
(6-10 Hours before)
|During Standing Heat
(can last 6 – 24 hours)
|After Standing Heat
(up to 10 hours)
|Will not stand to be ridden||Stands to be ridden||Will not stand to be ridden|
|Vocal and smells other cows||Nervous and restless||Clear Mucous discharge|
|Nervous and restless||Congregates and rides other cows||-|
|Attempts to ride other cows||Vulva moist, red and slightly swollen||-|
|Vulva moist, red and slightly swollen||Clear mucous discharge||-|
Heat Detect and Time AI (TAI) Protocols
These protocols include a combination of both heat detection and timed insemination. Heifers observed in heat should be inseminated 12 hours after standing heat. After approximately 3 days of heat detection, all heifers not showing heat after PG injection will be given an injection of GnRH and inseminated (i.e. timed insemination). The amount of time spent on heat detection is reduced and early responders have a better chance of conceiving compared to a single fixed-time AI. The Heat Detect and Timed AI protocols include:
- Select Synch + CIDR® & TAI
- MGA® - PG & TAI
- 14 – day CIDR® - PG & TAI
Fixed-Timed AI (TAI) Protocols
In a fixed-time AI protocol, all heifers are inseminated at a pre-determined time with no heat detection required. These protocols are typically more intensive and expensive, but no time is dedicated to heat detection. However, expect a lower conception rate compared to the previous protocols. When considering these fixed-time AI protocols, only synchronize the number of heifers that can be inseminated in a 4 hour period (protocol dependent). Fixed-Time AI protocols include:
- Short Term Protocols:
- 7-day CO-Synch + CIDR®
- 5-day CO-Synch + CIDR®
- Long Term Protocols:
- 14-day CIDR® - PG
- MGA® - PG
Handling and Administering Synchronization Hormones
When handling all hormones including the CIDR®, wear latex or non-latex gloves regardless if you are a man or a woman. Prostaglandin is a smooth muscle contractor; our intestines are the largest smooth muscle in the human body. If prostaglandin is absorbed through the skin it can “tie up” the digestive system. Additionally, the hormone functions in the human body like it does in a heifer or cow therefore, extreme care should be taken when handling all synchronization hormones.
Follow the protocol, give the proper hormone injection or insert at the right time and don’t expect to jump start all heifers that are not cycling. When administering injectable hormones, follow Beef Quality Assurance guidelines.
The adage more is always better does not work with melengestrol acetate (MGA). First, it is illegal to use MGA off label. Secondly MGA is absorbed in the fat and will take longer to clear from the heifer’s system when fed at a rate higher than 0.5 mg per head per day creating problems with estrus (heat) responses and subsequent timing of prostaglandin injection.
The addition of a progestin such as CIDR® in the protocol can help jump-start some of the non-cycling heifers. However, caution needs to be taken, CIDR® or MGA® are not the “cure all” for underdeveloped non-cycling heifers. An evaluation of the nutrition program is recommended if a high percentage of heifers are not cycling.