Breeding in Goats

Natural service is the easiest and most common breeding system for goats. Most hobby operations have a low buck:doe ratio (1:5) because of multiple breeds and different bloodlines. Bucks have a strong libido and can breed far more does than this (up to 1:50), although as they get older, and especially during the off-season, they are less efficient.

Artificial insemination (AI) is increasingly being used by goat producers because it allows for dissemination of valuable genetics and control of sexually transmitted diseases, and it eliminates the need to house a buck (see artificial insemination image).

Artificial insemination, goat

Image

Goats can be artificially inseminated intra- or transcervically (left) or via laparoscopic insemination (right) to inject semen directly into the uterus.

Courtesy of Dr. Jamie Stewart.

Proper heat detection and/or hormonal synchronization of the estrous cycle is essential and may lead to increased labor and costs. Ovulation in does occurs toward the end of standing estrus; therefore, insemination must occur around this time to be effective.

The AM-PM rule is generally used when breeding does based on estrus. If the doe is first noticed to be in standing heat in the morning, AI should be performed in the evening (or vice versa). However, breed-specific estrus durations should be considered when deciding the best time to inseminate based on heat.

If breeding is based on heats, owners should still consider having an intact or teaser buck on site to promote the expression of estrual behaviors in the does. If no buck is on site, buck-scented items (acquired from other goat owners) can be used to assist with performing heat detection.

Vaginal (pericervical deposition) or cervical (intracervical deposition) insemination techniques are inexpensive and easy to perform and can result in acceptable pregnancy rates if fresh or cooled-extended semen is used in high enough sperm concentrations (300 million and 100 million motile sperm, respectively) (1). However, if frozen semen is used, transcervical or laparoscopic intrauterine insemination techniques should be used.

Transcervical intrauterine insemination can be performed by experienced veterinarians or trained farm personnel and is a relatively quick and inexpensive procedure.

Laparoscopic intrauterine insemination typically yields greater pregnancy rates than transcervical, as it allows for the direct deposition of semen into the doe's uterine horn. However, this technique is more expensive, as it requires specialized equipment and more highly trained veterinarians to perform.

Frozen semen in 0.25–0.5 mL straws may be purchased directly from buck owners, stud companies, or custom collectors. Straws should contain a minimum concentration of 180 million motile sperm after thawing to be used transcervically, although lower concentrations (20 million) are acceptable if laparoscopic insemination is performed.

If farm personnel are trained to perform transcervical insemination, does can either be synchronized for fixed-time AI or bred based on heats. Synchronization of estrus is useful when performing laparoscopic insemination due to the amount of time it takes to set up the laparoscopic equipment and the associated costs.

Due to the costs associated with laparoscopic AI, utilizing teaser bucks to ensure that does are in heat at the time of the procedure is strongly recommended. Additionally, housing teaser bucks with does to be inseminated is thought to help improve overall pregnancy rates for AI due the influences of buck scent and behavior on time to ovulation in does.

The use of frozen semen in goats has expanded greatly since the early 2000s. Frozen semen for insemination can be purchased from established stud companies, but there are also companies that will perform custom collections to preserve genetics.

Semen collection via artificial vagina (AV) will produce higher-quality samples to be used for breeding, though samples collected by electroejaculation can also be acceptable.

For collecting via AV, most bucks will mount a doe in estrus and ejaculate into an AV with minimal training. Bucks can also be trained to mount a phantom or wethers to produce semen year-round.

The optimal sperm concentrations to freeze semen depend on the individual buck and production settings, though they should be approximately 200–400 million/mL to account for an approximate 50% death and damage rate during semen processing and thawing (2).

Most semen companies will have their own extender formulas, but commercially available extenders that can be prepared as needed can be used for custom collections on a smaller basis.

The use of non-egg-yolk-based extenders (eg, soybean lecithin) is preferred in bucks, because their seminal plasma contains a protein that coagulates when in contact with egg yolk protein. If egg yolk extenders are preferred, then semen should be centrifuged to remove seminal plasma secretions, which may also lead to a loss of spermatozoa.

There is no legislation or industry-wide standard in North America that governs the collection, processing, and sale of frozen semen in goats; however, country-specific legislation should be reviewed and followed if exporting semen.

Embryo flushing and transfer allow for dissemination of valuable female genetics. Their application in goats was previously limited because of the variable response of does to superovulation techniques and the need to perform these techniques surgically.

Newer protocols for embryo flushing and transfer have been developed that first stimulate does to ovulate, so superovulation (via administration of FSH) occurs during the follicular wave that is initiated on day 0 of the estrous cycle (after ovulation). Either natural copulation or laparoscopic insemination is then performed on the subsequent ovulation that is induced after superovulation.

Embryos can be retrieved by performing a uterine flush surgically, laparoscopically, or transcervically. Historically, surgical techniques were thought to produce the highest recovery rates, but with the continued development of nonsurgical techniques, comparable rates have been anecdotally reported.

When a veterinarian is performing surgical embryo recovery, ovaries should be examined laparoscopically before flushing to confirm that superovulation occurred (via visualization of multiple corpora lutea) to prevent unnecessary surgery. Embryos should be examined, graded, and washed under a microscope using similar standards and procedures as described in cattle.

Embryos can then either be transferred immediately via laparoscopic or surgical techniques into synchronized does (with the presence of corpora lutea confirmed via laparoscopy) or frozen in liquid nitrogen for indefinite storage.