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Breeding PracticesInbreeding v. Outcrossing and how Owlhaven uses this information to make breeding decisions.
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Owlhaven's Breeding Practices
Two common breeding practices are inbreeding and outcrossing. Inbreeding is practiced industry-wide with Nigerian goats. For example, historical Nigerians were inbred in order to develop the distinctive dairy style that they have today. Excessive inbreeding has been shown to lead to milk depression in dairy cattle and genetic defects in dogs. Outcrossing is often used to remedy the effects of inbreeding, to produce "hybrid vigor."
About OutcrossingOutcrossing is often used to bring new, desirable traits into a herd or to increase vigor. It increases genetic diversity and thus reduces the likelihood of the resulting individual being subject to disease or genetic abnormalities. Defects may still occur if animals are not carefully screened in advance (it won't necessarily correct existing genetic flaws). A disadvantage is that the outcomes are less predictable. Moreover, it may increase the time required to achieve your goals as a breeder. An example of an exceptional outcross is SGCH Dill's XM Keena 4*M EX92 (EEEE), an ADGA Reserve National Champion Doe.
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About InbreedingInbreeding is practiced in order to improve predictability of certain traits. For example, to try to ensure that all offspring have strong medial suspensory ligaments. Care must be taken in selection because both good and bad traits are transmitted when genetics become concentrated through inbreeding. Research on dairy cattle has found that milk depression begins at 12.5%. It is not unusual to find Nigerians that are inbred by as much as 30%-60%. With care linebreeding (a term sometimes used for lower levels of inbreeding) can produce exceptional animals such as Dill's GA Whiskey Lullaby 4*M EX91 (EEEE) at 14% and SGCH Castle Rock Owl's Clover EX90 (VEEE) at 12%. However, in most cases, care must be taken when making breeding decisions with does that are inbred at these levels to bring the inbreeding coefficient down in the next generation. For more information about inbreeding coefficients: www.instituteofcaninebiology.org/blog/coi-faqs-understanding-the-coefficient-of-inbreeding
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Owlhaven uses COI primarily as a diagnostic. Here are the steps that I might follow in a typical breeding season:
*A statistical measure of the degree of inbreeding.
- Check Kintraks for Inbreeding Coefficients* (COIs) for various buck/doe combinations, rule out any COIs above 15% in 10 generations.
- Use ADGA Genetics to compare Linear Appraisal scores for sire, dam, and paternal granddam for breedings. What needs to be strengthened in the doe? Will the buck be able to accomplish this?
- I keep a spreadsheet that includes the Linear Appraisal scores for the buck/doe combinations that I've researched. Over time that speeds the process.
- Develop short list of breeding combinations.
- Go back to Kintraks, check top contributors to inbreeding. Are any of the top contributors worrisome? What are their strengths (as demonstrated by progeny performance in ADGA Genetics)? What are their weaknesses?
*A statistical measure of the degree of inbreeding.