From: doconnor@sedona.intel.com (Dennis O'Connor)
Newsgroups: rec.equestrian
Subject: Re: interbreeding (was: help need friend)
Date: 29 Jul 92 04:06:25 GMT
Distribution: usa
Organization: Intel i960(tm) Architecture
In-reply-to: tracy@scoraz.resp-sci.arizona.edu's message of 28 Jul 92 06:44:38 GMT


tracy@scoraz.resp-sci.arizona.edu (Tracy Scheinkman) writes:
]
]	 Perhaps your wife's text book is correct, perhaps not (being in
] a textbook does not necessarily make info correct

Well, I did say that. 

] But please give me credit for at least remembering correctly the info on
] the 3 species of zebra and the quagga 

Sure ! Heck, I typed info in on those right out of a book only a few
days ago and already I don't rememberas much as you have !

]	 The info on the Tarpans I quote from Simon and Schuster's
] Guide to Horses and Ponies, "The Tarpan is regarded as the progenitor of
] all lightly-built breeds now in existence, although it is itself extinct.
] The last member of the breed living in the wild died in 1879 in a 
] desperate attempt to avoid capture, and the last Tarpan in captivity died
] in Munich zoo in 1887.  It was a difficult pony to tame for use in 
] agriculture.  There were two distinct types of Tarpan, one living on the 
] steppes, and the other in forested areas.  Both strains lived in the wild
] in Eastern Europe, from Poland to the Ukraine.  In an attempt to restore
] the breed the Polish government commandeered all horses displaying
] features similar to those of the Tarpan, and put them into the forests of
] Popielno and Bialowieza."  The reserve you saw must have gotten its 
] horses from stock that originated with these.

Perhaps. But the sign on the fence around the pasture said they had 
( and were cntinuing to ) try to recreate Tarpans by selective breeding,
starting with some kind of non-Tarpan stock. Anyone else been to the
Catskill Game Farm remember any more ? Its a fun visit, BTW.

] I would at least like to understand how offspring from this cross,
] modern horse with Przewalski's horse, can be fertile as it defies
] biological explanation.  

Well, I can give you the book's explanation of why most Equid crosses
are NOT fertile :

	"The Horse", ISBN 0-7167-0491-9

	Authors : J. Warren Evans, Assoiate Professor, U.C.Davis
		  Anthony Borton, Associate Professor, U.Mass
		  H.F.Hintz, Associate Professor, Cornell U.
		  Dale Van Vleck, Professor, Cornell U.
	Copyright 1977
	Published by W.H. Freeman and Company, New York and San Francisco
   [ BTW, I mainly give this info to in case someone wants to order a copy ]

page 438:

	"... Hybrids are apparently viable because the chromosome
	material is similar enough for all species, but the hyrids
	apparently cannot produce functional gametes because of
	synaptic failure due to rearrangement of the chromosome
	sets (Benirschke and Malouf, 1967). ..."

You'd have to check a library to find out what the reference is to. Sorry.

I checked "Animal Genetics", (c) 1982, ISBN 0-471-08497-2, and it
on page 395 mentions a fertile "interspecific" hybrid in cattle,
a cross between European cattle ( _Bos taurus_ ) and zebus ( _bos indicus_ )
but I don't know what the chromosome count for each is. Anyone ? They also
mention "cattalo", a cross between _Bos taurus_ and _Bison bison_
( American bison ), and state that the male hybrids are infertile,
but the female hybrids are not : interesting !

It seems to me that just a difference in chromosome counts isn't
enough to make a hybrid infertile, but I don't know what is !

Well, if you can make sense of all this, that would be great. I'm
just amazed at the complexity of it all.




Granted my
] B.S. was conferred in 1979 but something of what I learned then must
] still be correct.  Were the horses that crossed with the quarter horse
] mare Asiatic Wild Horses who have a different chromosome number from
] modern horses or Tarpans who have the same number of chromosomes (I
] believe).  Please educate me, anyone with solid info.)
]
]				 Tracy and everybody
]
--
Dennis O'Connor			doconnor@sedona.intel.com