The Beef Reproductive Task Force has released its 2017 recommended synchronization protocols for beef producers.
"These recommendations are designed to optimize pregnancy rates," said Taylor Grussing, SDSU Extension Cow/Calf Field Specialist.
Recommendations are based on review of current research and field-use of bovine estrous synchronization protocols.
Two sets of protocols are released. One for cows and one for heifers. "This is due to the physiological differences in the timing of key events, such as ovulation," Grussing explained.
The protocols are outlined for step-by-step instructions of how to carry out each synchronization protocol, detailing the number of days required for each protocol, products needed and timing for each step. The 2017 protocols can be viewed at the UNL website.
Three different protocols
Beef producers can choose from between 3 types of synchronization protocols for cows:
- Heat Detection: Select Synch, Select Synch + CIDR®, PG 6-day CIDR®
- Heat Detection and Time AI: Select Synch & TAI, Select Synch + CIDR® & TAI, PG 6-day CIDR® & TAI
- Fixed-Time AI: 7-day CO-Synch + CIDR®, 5-day CO-Synch + CIDR®
Heat Detection: Heat detection protocols work by setting cows up to show visual estrus and then to be bred by an AI technician 12 hours after the onset of standing heat.
In order for heat detection protocols to return acceptable pregnancy rates, cows need to be frequently monitored for visual signs of estrus.
Check cows at least three times per day for a half hour each time, with extra time spent detecting heat at sunrise and sunset as research shows that 56 percent of cows show heat from 6 p.m. to 6 a.m.
Heat detection aids are also available to assist in identifying cows in heat when no one is watching.
For this reason, when using a heat detection protocols, it is important to train people to look for specific signs of estrus behavior in order to detect cows coming into estrus, during estrus and after estrus (Table 1).
Heat detection & Time-AI: Heat detection and Time-AI protocols are the same as heat detection protocol steps with the exception of the shorter duration of time for heat detection.
After the three days of heat detection, any animals that have not shown signs of estrus are given an administration of GnRH (product that causes ovulation to occur within 30 hours) and fixed-time AI at that time.
Even though these cows may not be showing visual estrus, there is a possibility that fertilization can still occur.
Fixed-Time AI: Fixed-Time AI protocols are designed to breed all cows at a predetermined time as these protocols synchronize ovulation and not necessarily visual estrus.
These protocols are more labor intensive and expensive than the previously described protocol categories, as they require more trips through the chute and injections. However, there is no heat detection with fixed-time AI, so the value of labor saved not heat detecting can go towards funding these more intensive protocols.
Cow Criteria
In order for these recommended protocols to be most effective, cows should meet some minimum qualifications before beginning an estrous synchronization protocol.
Body condition score (BCS) is important for reproductive efficiency. Cows should be in a BCS of 5 at protocol initiation. Also, cows should be 50 days postpartum before starting protocols.
By waiting 50 days after calving, cows should have completed uterine involution and resumed fertile estrous cycles which will give them better chances of conceiving than if started earlier.
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