Hybrid vigor

Hybrid
vigor is a term scientists use to refer to the observation that the
offspring of two unrelated parents are often larger and healthier
than more inbred offspring.  Cornish
Cross chickens
are an extreme example of hybrid vigor, but I was curious to see
whether I’d notice any difference between the purebred Australorp
chicks we raised this year and the Australorp X Marans chicks.



The first thing I noticed is
that the speckling on Cuckoo Marans seems
to be a sex-linked trait.  Australorp X Marans pullets (girls)
aren’t speckled, while the cockerels (males) invariably are. 
Since I didn’t keep track of which eggs hatched into which pullets, I
can’t tell you about hybrid vigor among the girls since they looked
just like the purebred Australorp girls.  Among the males, though,
the Australorp X Marans hybrids averaged 12% heavier.



The results aren’t
really conclusive, though.  In addition to my small sample size,
there’s another factor I can’t
really disentangle — whether what I’m seeing is hybrid vigor or
whether Cuckoo Marans just bulk up faster than Australorps.  My
data from when I was raising each as a pure breed isn’t really
comparable — the two breeds were in very different pastures and on
different
rations.



Scientific or not, my
glimpse into the possibility of hybrid
vigor suggests that it’s worth keeping a mixed flock of parent birds
when raising your own broilers.  I suspect that in the long run, a
constantly changing mutt flock might be better for our purposes than
any single heirlom variety.