Friday, January 31, 2014
WHY AI IS MORE DIFFICULT IN SHEEP THAN OTHER LIVESTOCK
 |
| Comparison of the longitudinal section of the cervix of a ewe (left) and doe (right). Notice the pronounced folds near the bottom (external os) of the ewe's cervix. The canal turns 180 degrees and therefore prevents direct passage of a pipette. |
One of the major reasons AI (artificial insemination) is more difficult in sheep, than it is in other livestock, is the anatomical structure of the ewe's cervix. The cervix is 4-7 cm long and connects the uterus to the anterior vagina. The interior wall of the cervix has a number of ridges and crypts which helps to keep infection out. In the ewe, however, these folds are more pronounced, irregular in shape, and fit so closely together that an inseminating pipette is virtually impenetrable.
Evans,
Gareth, and M. Chisholm Maxwell. "Anatomy of the Female Reproductive Tract." Salamon'sArtificial Insemination of Sheep and Goats. Butterworths, 1987. 34-35.
Friday, January 24, 2014
Our Team and Project
 |
| Ginger Davidson, Jeff Bielek, Kathy Bielek, Don Brown, Ann Brown, Craig Zimmerly, Dale Duerr |
In this two year project, a team
of farmers and veterinarians are investigating a farmer-friendly, low cost
artificial insemination (AI) technique.
Although numerous research studies have been conducted on AI in sheep,
the application of AI at the farmer level is limited. Such knowledge would allow large segments of
the sheep industry to make genetic progress similar to other livestock
industries. AI is currently being used in other livestock species with
tremendous success by allowing semen from high quality sires to be disseminated
over larger populations of females allowing for faster genetic progress with decreased
biosecurity risk.
AI in sheep is inherently more
complicated due to difficulty in preserving the ram’s semen and the anatomic
complexity of the ewe’s cervix. Team
members will be trained on proper collection and handling of semen, as well as
vaginal insemination techniques.
Conception rates will be monitored over two years.
Semen extenders are used to
dilute the semen, allowing it to effectively cover more ewes, as well as provide
nutrients for the sperm and protect against chilling, thus extending the
viability of the semen. One of the challenges with sheep is that ram semen has
proven difficult to extend beyond 24 hours in the past, making shipment of
fresh semen for long distances impractical.
The team will use recent research and new extenders, to extend the
viability of fresh semen beyond 24 hours which would allow more options for use.
Thursday, January 16, 2014
How can artificial insemination (AI) further parasite resistance in sheep?
Joan Burke
(USDA, ARS), Stephan Wildeus (Virginia State University), Roxanne Newton (Hound
River Farms), Kathy Bielek (Misty Oaks Farm)
The only growing sector of the sheep industry has been smaller forage-based farm flocks east of the Mississippi, particularly in the south (NASS, 2011). This increase is primarily due to the introduction of Katahdin hair sheep since they are hardy, well adapted to forage-based systems, and have greater resistance to parasites compared with traditional wool breeds. To ensure future growth and sustainability, small farmers must have access to sires with superior genetics for economically important traits such as milk production and growth. Equally important is access to sires with known resistance to health related problems such as hoof rot and parasitism, both heritable traits. The use of Estimated Breeding Values (EBVs) (see NSIP.org) allows for the selection of these superior animals, but a method is needed to share these genetics across more animals and/or flocks.
It is often difficult, especially for small flocks, to justify the purchase price of a superior ram, yet the success of these flocks, and the sheep industry as a whole, requires this advancement. The widespread use of artificial insemination (AI) in the cattle, swine, and poultry industries has resulted in accelerated genetic progress for economically important traits, while minimizing exposure to animal diseases. The use of AI would also improve biosecurity, alleviate transportation costs associated with moving live animals, and reduce the risk of heat-stress related sterility of rams that often occurs during transport in late summer, particularly in the south. However, there is limited use in the small ruminant industry due to cumbersome AI procedures.
It is often difficult, especially for small flocks, to justify the purchase price of a superior ram, yet the success of these flocks, and the sheep industry as a whole, requires this advancement. The widespread use of artificial insemination (AI) in the cattle, swine, and poultry industries has resulted in accelerated genetic progress for economically important traits, while minimizing exposure to animal diseases. The use of AI would also improve biosecurity, alleviate transportation costs associated with moving live animals, and reduce the risk of heat-stress related sterility of rams that often occurs during transport in late summer, particularly in the south. However, there is limited use in the small ruminant industry due to cumbersome AI procedures.
Historically, AI in the U.S. has been limited in sheep due to the complexity of the ewe’s cervix and because of difficulties in storing and thawing frozen semen. Laparoscopic or surgical AI has been used successfully to bypass the cervix, but is a veterinary procedure that is cost-prohibitive and not accessible to most small farmers. Vaginal AI is a low technology procedure that can be accomplished using fresh semen with reasonable pregnancy rates. There is potential to train farmers to use this technique. Moving sheep production into the future on small and mid-sized farms will depend on the development of a farmer friendly AI program using superior genetics and is also cost-effective for farmers.
A vaginal procedure was previously developed using prolific sheep breeds in Norway (Paulenz et al., 2002, 2005) and at Virginia State University (VSU, Wildeus, 2012). In the Norway research, conception rates were 63% using liquid semen with 150 × 106 spermatozoa on 52 farms (2002), and lambing rates ranged from 56 to 83% among 10 farms and 58 to 78% among 6 rams using 200 × 106 spermatozoa (2005). Results at VSU indicated that pregnancy rate of yearling ewes was 75%, and 59% using fresh or 39% using 12-hour stored semen in mature ewes (Wildeus, 2012). Mook et al. (2008) at VSU indicated that fertility after fresh and 72-hour stored liquid semen extended with Tris-egg yolk using the vaginal AI procedure was similar to intrauterine AI. The Norway group and Wildeus (2012) used a skim milk/egg yolk extender; this was compared with the Tris-egg yolk extender, which reduced fertility (Paulenz et al., 2003). Optimizing the semen extender may increase sperm viability and conception rates. Preliminary results of a SARE on-farm study in Ohio using vaginal AI in Katahdin ewes indicated conception rate of 50% (Bielek, personal communication).
Prolific breeds such as the Katahdin or St. Croix should have higher success with vaginal AI than less prolific breeds. There were 8,131 registered Katahdins, the second highest breed rank in 2012, and 42 Katahdin flocks enrolled in NSIP (www.nsip.org). NSIP creates an annual elite sire report including updated EBVs of more than 120 mature rams and more than 1300 yearling rams (September 2013 report). ARS has a working relationship with many of these flocks and will be able to obtain semen from elite rams from this report. The Dorper, Dorset, and Southdown breeds are prolific breeds included in the top six registered breeds, and the Polypay and Dorset have several breeders included in NSIP which could be considered for future AI studies. There is considerable opportunity to conduct research on AI in these breeds.
In summary, technology that includes AI by farmers who use select sires will be able to accelerate progress on heritable traits and minimize risk of disease transmission. The acquisition of sheep that are uniquely suited to the southeastern U.S. will provide increased marketing opportunities for farmers, even cattle producers adding diversity to their farm.
Literature cited
Mook, J.L., Collins, J.R. and Wildeus, S. 2008. Retention of sperm motility, viability and fertility in ram semen after liquid storage at 4°C for up to 96 hours. J. Anim. Sci. 86 (Suppl. 2):496-497.
NASS (National Agricultural Statistics Service). 2011. Sheep and Goat Report. , Agricultural Statistics Board, USDA, Washington, D.C.
Paulenz, H., Ådnøy, Fossen, O., Söderquist, L., T., Berg, K.A., 2002. Effect of deposition site ans sperm number on the fertility of sheep inseminated with liquid semen. Vet. Rec. 150:299-302.
Paulenz, H., Söderquist, L., Ådnøy, T., Fossen, O., Andersen Berg, K., 2003. Effect of milk and TRIS-based extenders on the fertility of sheep inseminated vaginally once or twice with liquid semen. Theriogenology 60:759-766.
Paulenz, H., Söderquist, L., Ådnøy, T., Nordstoga, A.B., Andersen Berg, K., 2005. Effect of vaginal and cervical deposition of semen on the fertility of sheep inseminated with frozen-thawed semen. Vet. Rec. 156:372-375.
Wildeus, S., 2012. Pregnancy rates in hair sheep ewes following vaginal insemination with fresh and short-term stored liquid semen. Reprod. Domest. Anim. 47 (Suppl. 4): 422.
NASS (National Agricultural Statistics Service). 2011. Sheep and Goat Report. , Agricultural Statistics Board, USDA, Washington, D.C.
Paulenz, H., Ådnøy, Fossen, O., Söderquist, L., T., Berg, K.A., 2002. Effect of deposition site ans sperm number on the fertility of sheep inseminated with liquid semen. Vet. Rec. 150:299-302.
Paulenz, H., Söderquist, L., Ådnøy, T., Fossen, O., Andersen Berg, K., 2003. Effect of milk and TRIS-based extenders on the fertility of sheep inseminated vaginally once or twice with liquid semen. Theriogenology 60:759-766.
Paulenz, H., Söderquist, L., Ådnøy, T., Nordstoga, A.B., Andersen Berg, K., 2005. Effect of vaginal and cervical deposition of semen on the fertility of sheep inseminated with frozen-thawed semen. Vet. Rec. 156:372-375.
Wildeus, S., 2012. Pregnancy rates in hair sheep ewes following vaginal insemination with fresh and short-term stored liquid semen. Reprod. Domest. Anim. 47 (Suppl. 4): 422.
Saturday, December 14, 2013
Webinar on Profitable Genetic Selection
Reserve your spot at the upcoming webinar entitled:
"Profitable Genetic Selection: How the National Sheep Improvement Program (NSIP) Can Help the US Sheep and Goat Industry".
Reid Redden, Ph.D., North Dakota State University extension sheep specialist and NSIP chair, will present this information at 7 p.m. EST on Dec. 17.
Reid Redden, Ph.D., North Dakota State University extension sheep specialist and NSIP chair, will present this information at 7 p.m. EST on Dec. 17.
To register:
https://attendee.gotowebinar.com/register/3280183289165496321.
NSIP is a nonprofit organization created to develop genetic predictors for production traits relevant to the U.S. sheep and goat industries. This technology generates estimate breeding values (EBVs) based on performance data that is submitted by participating flocks.
The program develops EBVs for:
* growth traits: birth, weaning (60 d), post-weaning (120 d), and yearling (365 d) weights,
* reproductive traits: number of lambs born and weaned,
* carcass traits: loin muscle and back fat depth,
* wool traits: fleece weight, fiber diameter, and staple length and
* parasite resistance: weaning fecal egg count.
NSIP is a nonprofit organization created to develop genetic predictors for production traits relevant to the U.S. sheep and goat industries. This technology generates estimate breeding values (EBVs) based on performance data that is submitted by participating flocks.
The program develops EBVs for:
* growth traits: birth, weaning (60 d), post-weaning (120 d), and yearling (365 d) weights,
* reproductive traits: number of lambs born and weaned,
* carcass traits: loin muscle and back fat depth,
* wool traits: fleece weight, fiber diameter, and staple length and
* parasite resistance: weaning fecal egg count.
In addition, indexes are created that rank the most important traits for the respective breed.
EBVs are calculated by making comparisons of lambs among their flock mates; therefore, lambs that outperform their flock mates get positive values for the particular trait and genetically related traits. Additionally, sire and dam EBVs increase for production of a lamb that is above or below flock average (progeny test).
To better serve the entire industry, NSIP needs more seedstock producers to enroll, use the program to its full capacity and work with other NSIP breeders to develop genetic connections within the breed. It requires that commercial producers request that their seedstock providers deliver this data and purchase sheep with EBVs that are consistent with the needs of the flock.
In summary, NSIP can help the industry make more informed and reliable breeding decisions and lead to more productive and profitable sheep and goat industries.
This webinar is made possible with funding support from the American Sheep Industry Association and the Rebuild the Sheep Inventory Committee.
After registering, you will receive a confirmation email containing information about joining the webinar.
EBVs are calculated by making comparisons of lambs among their flock mates; therefore, lambs that outperform their flock mates get positive values for the particular trait and genetically related traits. Additionally, sire and dam EBVs increase for production of a lamb that is above or below flock average (progeny test).
To better serve the entire industry, NSIP needs more seedstock producers to enroll, use the program to its full capacity and work with other NSIP breeders to develop genetic connections within the breed. It requires that commercial producers request that their seedstock providers deliver this data and purchase sheep with EBVs that are consistent with the needs of the flock.
In summary, NSIP can help the industry make more informed and reliable breeding decisions and lead to more productive and profitable sheep and goat industries.
This webinar is made possible with funding support from the American Sheep Industry Association and the Rebuild the Sheep Inventory Committee.
After registering, you will receive a confirmation email containing information about joining the webinar.
Breeding Soundness Exams
While the focus of our project is Artificial Insemination, our work first focused on the the ram by learning about breeding soundness exams (BSE). A BSE is a relatively simple test to evaluate a ram’s suitability for breeding. This test is of value to every sheep operation and is essential for rams used in AI. It consists of a physical examination, an inspection of the reproductive organs, and an evaluation of a semen sample.
Dr. Craig Zimmerly, DVM is demonstrating the correct use of a scrotal tape as part of this ram's BSE. Research has shown that rams with large scrotal measurements not only produce
more semen than rams with smaller scrotal measurements but will also have
progeny that reach puberty earlier.
The Society for Theriogenology recommends the following breeding program standard values for scrotal circumference:
Rams 8 months to 14 months
< 30 cm questionable
30 - 36 cm satisfactory
> 36 cm exceptional
Rams > 14 months old
< 32 cm questionable
32 - 40 cm satisfactory
> 40 cm exceptional
Wednesday, December 4, 2013
Performing Sheep AI on the Farm
Kathy Bielek of Misty Oaks Farm, is being coached by Dr. Dale Duerr, DVM on the proper pipette position while she inseminates one of her Katahdin ewes. This is one of 3 farms visited by our team in the past 3 months. At each farm, 20 ewes have been artificially inseminated.
Dr. Duerr, DVM and Dr. Zimmerly, DVM have taught us about performing breeding soundness exams (BSE) on rams, handling semen, prepping ewes, inseminating ewes using cervical AI techniques, and performing ultrasounds to determine pregnancy.
This project team was formed when a small group of farmers realized there was a need to not only have a biosecure method for introducing new genetics to closed flocks but also to share their genetic gains across more flocks. Although numerous research studies have been conducted on AI in sheep, the application of AI at the farmer level in the U.S. is limited. We are hopeful that this can change.
Monday, December 2, 2013
Artificial Insemination Methods Used in Sheep
Insemination of sheep may be vaginal, cervical (posterior or transcervical), or intrauterine.
Vaginal insemination deposits fresh diluted semen into the anterior of the vagina without an attempt to locate the cervix. It is the simplest and easiest method but requires a larger dose of semen and the success rates are usually less than other methods.
Posterior cervical insemination uses a pipette to transverse the vagina and deposit fresh diluted semen at the cervical opening. It is a technique that is relatively easy to perform, but is limited to fresh semen (diluted or undiluted) since conception rates are generally lower with frozen semen. It is the most common method used in sheep.
Trancervical insemination is performed by inserting a thin pipette through the cervix and depositing the sperm directly into the uterus. Because of the anatomic complexity of the ewe’s cervix, it is more difficult to perform than posterior cervical AI. This method requires a special pipette but allows the use of either fresh or frozen semen at fairly high success rates.
Intrauterine insemination is often referred to as laparoscopic artificial insemination (LAI) and is accomplished by depositing semen directly into the uterus through an abdominal incision. Conception rates are typically very high. Because LAI is an invasive procedure, it requires the expertise of a trained veterinarian which makes it cost-prohibitive and less available for producers.
