Based on the research and demonstration work of Dr. Charlotte Farin and William Knox, North Carolina State University, and Dr. Niki Whitley, The Cooperative Extension Program at North Carolina A&T State University
Estrus synchronization combined with artificial insemination (AI) is used regularly in cattle and has been useful for breeding management. These technologies would also be useful for goat farmers interested in using AI to increase the genetic merit of offspring. Estrus synchronization reduces the amount of time required for checking estrus (heat) before AI. However, using timed AI (TAI) so that all animals are bred the same day without heat checking is even more efficient, saving time, money, and labor. Some advantages to timed AI include:
- No heat checking is used.
- Semen storage may not be needed.
- If an AI technician is being hired, a single trip can be scheduled.
The key for effective timed AI is the synchronization of not just estrus but also of ovulation (egg release). In recent research and demonstration projects at North Carolina State University (NCSU) and North Carolina A&T State University (NCA&TSU), ovulation synchronization methods for timed AI were compared.
At NCSU, Boer does that had kidded at least once before were assigned to either traditional estrus synchronization with AI following heat checking (Heat Check) using the AM-PM rule (if in estrus AM, breed PM, and vice versa) or the ovulation synchronization method with timed artificial insemination (NC Synch). The NC Synch method was used with TAI and was developed based on Ov-Synch protocols used in cattle. The times between drug treatments were changed to better fit the reproductive responses of goats. Frozen semen from a commercial company (Superior Semen Works, Milton, NH) was used for all AI, and motility of samples was confirmed for each straw. The same technicians did the inseminations (with equal numbers for each technician in each treatment group).
Half of the animals followed the Heat Check method described below:
|
Days & Time |
Heat Check Method Procedures |
|
Day 0 |
Intramuscular injection 2 cc Lutalyse®* |
|
Day 10 |
Intramuscular injection 2 cc Lutalyse |
|
Day 10-17 |
Heat Check (18-24 hr. prior to breeding) |
|
Day 10-17 |
Breed (AI) by AM-PM rule |
*Not labeled for use in goats in the United States.
The remaining does were bred using the NC Synch with TAI method described below:
|
Days & Time |
NC Synch with TAI Method Procedures |
|
Day 0 |
Intramuscular injection 3 cc Lutalyse* |
|
Day 7 |
Intramuscular injection 1 cc Cystorelin®* |
|
Day 14 |
Intramuscular injection 3 cc Lutalyse |
|
Day 17 |
Intramuscular injection 1cc Cystorelin and AI |
*Not labeled for use in goats in the United States.
At about 50 and 85 days after artificial insemination, animals were checked for pregnancy status using transabdominal ultrasonography. After the artificial insemination breeding period, all animals were returned to the flock and managed through the standard operating procedures for the farm. Data on kidding, including number of females kidding to AI breeding date, number of kids born, number of kids born alive, and twinning rate, were recorded. This research was conducted for three years (2007 to 2010).
Pregnancy rates based on ultrasound at 50 and 85 days after breeding
Year 1 (2007-2008):
Heat Check: 15 does synchronized, 13 bred, 8 does pregnant.
NC Synch: 15 does synchronized and bred by TAI, 11 does pregnant.
Pregnancy rate for does in Heat Check group (8 of 15): 53%
Pregnancy rate for does in NC Synch group (11 of 15): 73%
Year 2 (2008-2009):
Heat Check: 26 does synchronized, 24 bred, 19 does pregnant.
NC Synch: 26 does synchronized and bred by TAI, 20 does pregnant.
Pregnancy rate for does in Heat Check group (19 of 26): 73%
Pregnancy rate for does in NC Synch group (20 of 26): 77%
Year 3 (2009-2010):
Heat Check: 25 does synchronized, 21 bred, 8 does pregnant.
NC Synch: 25 does synchronized and bred by TAI, 14 does pregnant.
Pregnancy rate for does in Heat Check group (8 of 25): 32%
Pregnancy rate for does in NC Synch group (14 of 25): 56%
All Years Combined:
Pregnancy rate for does in Heat Check group (35 of 66): 53%
Pregnancy rate for does in NC Synch group (45 of 66): 68%
Differences between years is not surprising given differences in weather and other variables that can change from year to year, though the exact reason for the much lower rates in Year 3 is not known.
At the Upper Mountain Research Station, NCSU, NCA&TSU, and station staff conducted a demonstration and applied-research project using 38 Boer-crossbred does. Half of the does underwent the NC Synch method developed at NCSU as described above, and the other half underwent a CIDR method as follows:
|
Days & Time |
CIDR®* Method Procedures |
|
Day 4 |
CIDR inserted |
|
Day 15 |
CIDR removed; intramuscular injection of 3 cc Lutalyse and 2.5 cc P.G. 600®* |
|
Day 17 |
AI (breed) |
*Not labeled for use in goats in the United States.
Does were housed together and were kept from sight, sound, and smell of all bucks until day 15 when all were allowed fence-line contact to an intact buck. All animals were bred by timed AI on day 17. Blood samples were collected 31 days after insemination to determine pregnancy status (BioPRYN® BioTracking, LLC). Pregnancy rates were higher for animals treated with the CIDR method (50%) than the NC Synch method (10.5%).
The low pregnancy rates associated with the NC Synch method in the Upper Mountain Research Station study may have resulted from an early ovulation in this group of does that had not been exposed to bucks prior to the start of the experiment. A follow-up study was conducted at NCSU using 87 Boer and Boer-crossbred does that were divided into four treatment groups: Heat Check method described above, CIDR Method described above, NC Synch with TAI at 48 hours after the second Lutalyse injection (NC Synch 48) and NC Synch method with TAI at 72 hours after second Lutalyse injection (NC Synch 72, the NC Synch protocol used previously). All does were exposed to bucks via fence-line contact prior to the start of any treatments. The results are shown below:
Heat Check: 22 does synchronized, 18 bred, 12 does pregnant.
CIDR: 22 does synchronized and bred by TAI, 10 does pregnant.
NC Synch 48: 22 does synchronized and bred by TAI, 2 does pregnant.
NC Synch 72: 21 does synchronized and bred by TAI, 11 does pregnant.
Pregnancy rate for does in Heat Check group (12 of 22): 55%
Pregnancy rate for does in CIDR group (10 of 22): 45%
Pregnancy rate for does in NC Synch 48 group (2 of 22): 9%
Pregnancy rate for does in NC Synch 72 group (11 of 21): 52%
These studies demonstrate the importance of making sure that AI occurs at the right time relative to the synchronized ovulation in TAI protocols. Because exposure to buck pheromones can shift ovulation timing in does that have not been in prior contact with bucks (known as the buck effect), it is important to be sure that does are managed carefully when considering the NC Synch TAI protocol.
A successful ovulation synchronization program with timed AI would allow farmers to add new, higher-value genetics into their herd more efficiently than with estrus synchronization and traditional AI. All breeding can occur on a single day that is selected by the farmer and/or AI technician, allowing for purchase and use of semen without long-term storage. These benefits allow for lower-cost, more efficient AI technology adoption.
Acknowledgments: Dr. Keesla Moulton, Elizabeth Bowdridge, Deanna Sedlak, Roberto Franco, Allison Cooper, Lorie Townsend, Ray Horton, and Joseph French.
References (peer-reviewed abstracts):
E. C. Bowdridge, W. B. Knox, C. S. Whisnant, and C. E. Farin. 2011. NC Synch: A protocol for ovulation synchronization and timed artificial insemination in goats. J. Anim. Sci. 89 E-Suppl. 1:658.
Whitley, N.C., C.E. Farin, W.B. Knox, L. Townsend, J.R. Horton, K. Moulton and S. Nusz. 2011. Comparison of two ovulation synchronization methods for timed artificial insemination in goats. J. Anim. Sci. 89 E-Suppl. 1:658.