§ 19
How quickly is inbreeding increasing in my breeding group?
Answer: In a small breeding group, inbreeding increases each generation, even if you never breed siblings. How quickly mainly depends on the sex with the fewest individuals. The effective population size (Ne) says what size an ideal population with equal sex distribution your group corresponds to. Inbreeding increase per generation is 1 ÷ (2 × Ne). FAO uses 1% per generation (Ne of at least 50) as an upper limit in the conservation of livestock breeds, and the same figure is often used in zoo and laboratory animal breeding.
Ne = 4 × hanner × hunner ÷ (hanner + hunner)
ΔF pr. generation = 1 ÷ (2 × Ne)
Indavl efter t generationer = 1 − (1 − ΔF)^t (startindavl sat til 0)
Only animals that actually have offspring count
| Symbol | Meaning | Unit |
|---|---|---|
| hanner | Breeding males (that actually get offspring) | stk |
| hunner | Breeding females (that actually get offspring) | stk |
| generationer | Number of generations forward | generationer |
| = | Effective population size (Ne) | dyr |
| = | Inbreeding increase per generation (ΔF) | % |
| = | Inbreeding after the chosen generations | % |
| = | Ne if the same animals were evenly distributed by sex | dyr |
Does not apply when
The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.
Substituted
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Du bruger den, når du arbejder med avl af forsøgsdyr eller af dyr i en zoologisk have, og skal vurdere, hvor hurtigt indavlen stiger. Den viser især, hvor meget det betyder, at der er få hanner i avlen.
Zooens surikatgruppe har 2 avlshanner og 10 hunner, der får unger. Du vil se 10 generationer frem.
It means: Gruppens Ne er kun 6.7 dyr, og indavlen stiger 7.5 % pr. generation. Efter 10 generationer er indavlen 54.1 %, så gruppen skal have nyt blod fra et avlsprogram.
En koloni af outbred rotter har 20 hanner og 20 hunner i avl.
It means: Ne er 40 dyr, og indavlen stiger 1.25 % pr. generation. Det er lidt over målet på 1 %, så flere avlspar ville hjælpe.
Et lille dyreanlæg har 1 han og 25 hunner.
It means: Ne er kun 3.8 dyr, selvom der er 26 dyr. Var dyrene fordelt ligeligt på køn, var Ne 26 dyr. Indavlen stiger 13 % pr. generation.
Ne er aldrig mere end fire gange antallet af det køn, der er færrest af.
Sammenlign med stambogens indavlskoefficienter. De rigtige tal fra stamtavlen går forud for overslaget.