From: ckw0@aber.ac.uk (Carl Keri Williams)
Newsgroups: rec.equestrian
Subject: Re: Need a Friend
Date: 21 Jul 92 21:16:16 GMT
Organization: University of Wales, Aberystwyth

In article <DOCONNOR.92Jul20132154@potato.sedona.intel.com> 
doconnor@sedona.intel.com (Dennis O'Connor) writes:
>
>blythedr@infonode.ingr.com (Dennis Blythe) writes:
>] I too am wondering what a burro is, also what is a "Jackass" ?
>
>Here's my fallible understanding
>
>Burro  : a small breed of the ass family
>Donkey : another small breed of the ass family
>Ass    : a breed of the ass family (suprise!), the "standard" size
>Onager (sp?) : a breed of the ass family larger than an ass
>Zebra  : a species of the ass family, with lotsa stripes
>
>I believe any of the above can interbreed with fertile offspring resulting.

Aarggh!  I'll have to go raid the library again - I knew I should have
taken some photocopies...

An onager is a separate species, not a breed.  There is a wild ass which is
also a separate species.  The term 'zebra' includes several species, which 
have different chromosome numbers.  There are a few other wild equids too,
like Przwalskys.  All the different species can interbreed, but the offspring
are sterile, except between Equus caballus (real horses) and Equus przvalski
who apparently manage to lose whatever extra chromosomes are kicking around
to get the numbers right again.  

Two of the equine species (can't remember which but I think they were two
of the rarer ones) had the same chromosome number, but I don't think
anyone has tried cross-breeding them.

In my own opinion (OK, so it may be just a tiny bit biased) I feel that the
Arabian may verging on being a separate species from other 'cold blooded'
horses.  They had the requisite isolation from foreign blood and developed 
into their own definate type with unique characteristics (except that I 
discovered that the rumour about the number of vertebrae being different is 
not correct :-( ).  Their chromosome number remained the same however, so 
they made a wonderful 'outcross' for other horses, giving them a terrific
dose of hybrid vigour (which is what makes mules tougher and stronger than
either horses or donkeys, and mongrel dogs seemingly immune to 'pedigree' 
type ailments).  

Of course by now there is scarcely a breed of horse left which hasn't been
improved by the use of the Arabian, which makes it more difficult to 
see the differences which must have been so apparant centuries ago.  The 
problem is that unless we are careful, all the old 'pure' breeds, including
not only the  Arabian but also things like Shetland ponies (the Scottish
variety, not the improved American sort), Exmoors, Caspians, Akal Tekes,
whatever, will either disappear or lose their natural toughness by being
bred purely for the showring.  Arabs are noted for their endurance, but 
how many champion show horses are ever tested 'properly'?  I think all the
pure breeds (as opposed to the created breeds like the Thoroughbred) should
be bred with the need to keep this inherent toughness there, so that when
the created breeds need another dose of good old hybrid vigour, the old
breeds are still there to give it and haven't degenerated into over-pretty
but useless parodies of their ancestors.

OK, I've rambled enough....

Flame away, I'd like some thoughts on this...

Esther
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