Breeding in Goats
Natural service is the easiest and most common breeding system. Most hobby operations have a low doe:buck ratio (5:1) because of multiple breeds and different bloodlines. Bucks have a strong libido and can breed far more does than this, 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. 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. However, if frozen semen is used, transcervical or laparoscopic intrauterine insemination techniques must be used, which 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.
Semen can be collected for AI 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. Older bucks are often reluctant to breed does that have had estrus induced outside the normal breeding season; therefore, collections are more successful when young bucks are used. The optimal sperm concentrations depend on the individual buck and production settings but should be ~200–400 million/mL to account for an approximate 50% death and damage rate during semen processing and thawing. There is no legislation or industry-wide standard in North America that governs the collection, processing, and sale of frozen semen, but country-specific legislations should be reviewed and followed before exporting semen.
Embryo transfer allows for dissemination of valuable female genetics. Its application in goats is somewhat limited because of the variable response of does to superovulation techniques. Control of the estrous cycle is crucial to ensure adequate timing for induction of superovulation, which is achieved by treating with commercially available follicle-stimulating hormone (FSH) products. Laparoscopic insemination of semen is recommended to confirm that superovulation occurred (via visualization of multiple corpora lutea) and to allow for the greatest conception rate. Embryo retrieval can be achieved surgically, laparoscopically, or transcervically, with surgical techniques providing the highest recovery rates. Embryos can then either be transferred immediately via laparoscopic or surgical techniques into synchronized does or frozen in liquid nitrogen.