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 both dissemination of valuable genetics and control of sexually transmitted diseases. 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: 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.
Vaginal (pericervical deposition) or cervical (intracervical deposition) insemination techniques are inexpensive and easy to perform and can result in acceptable pregnancy rates if fresh semen is used in high enough concentrations (300 million and 100 million motile sperm, respectively). However, if frozen semen is used, transcervical or laparoscopic intrauterine insemination techniques must be used. These techniques are more expensive and require more skilled personnel. Frozen semen in 0.25–0.5 mL straws may be purchased directly from buck owners 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. Synchronization of estrus is typically preferred when performing laparoscopic insemination to minimize costs by breeding multiple does in one session.
Courtesy of Dr. Jamie Stewart.
Semen can be collected for insemination in an artificial vagina or with an electroejaculator. Most bucks will mount a doe in estrus and ejaculate; with training they can ejaculate year-round and even mount wethers. The optimal sperm concentrations to freeze semen depend on the individual buck and production settings, though they should be ~200–400 million/mL to account for an approximate 50% death and damage rate during semen processing and thawing. Semen should be centrifuged if an egg yolk extender is used because of interactions with seminal plasma secretions that have toxic effects on spermatozoa. Non-egg yolk extenders are available and preferred by many for semen freezing in bucks to minimize semen losses that occur with centrifugation. There is no legislation or industry-wide standard in North America that governs the collection, processing, and sale of frozen semen; 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. Newer protocols have been developed that first stimulate does to ovulate, so that 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 are then performed on the subsequent ovulation that is induced after superovulation. Embryos can be retrieved surgically, laparoscopically, or transcervically, with surgical techniques providing the highest recovery rates. If possible, ovaries should be examined laparoscopically before flushing to confirm that superovulation occurred (via visualization of multiple corpora lutea). Embryos can then either be transferred immediately via laparoscopic or surgical techniques into synchronized does or frozen in liquid nitrogen for storage.
