Thanks! Maybe it wasn't lethal I read, sorry, still good info. Looking back at the article it was called "terminal cross" they were avoiding trying for hybrid vigor.
Quote: Some of that may be cross species confusion, too. White cats with blue eyes are often deaf - but some people will try to tell you that all white cats are deaf (not true). Also, there is a spotting gene in horses that can result in deafness (the horse may or may not be completely white). There is a lethal white gene in horses, too - the Lethal White Overo (also called Frame). There are also homozygous lethal color/pattern genes in rats and mice.
The broken (En) gene in rabbits is another gene that, while not lethal, often causes problems when an animal inherits it from both parents. In addition to the spotting on the coat that we see, this gene also affects the rabbit's digestive system, making it run a bit slower than normal, non-spotted rabbits' systems do. A rabbit with just one copy usually isn't affected much, and will probably be perfectly fine. The rabbit with two copies of the En gene has a dramatically slower digestive tract. Often, even when things are running along normally, the fecal pellets of the EnEn rabbit will be odd shapes and sizes. Normal rabbit poop is a bit like plain M&M's - round and slightly flattened, but all the same size and shape. The pellets of the double broken (called a "Charlie") are more like peanut M&M's - irregular sizes and shapes. Every rabbit is at some risk of developing digestive blockages/GI stasis, but these guys have a higher than normal risk. Many years ago, I had a Mini Lop doe that was a Charlie. Every time she kindled, her digestive system packed it in for a couple of days. I bred her 3 times before I figured out what the pattern was, and never after that.
The term "terminal cross" means that the offspring of that cross are all intended for slaughter; the productivity of that generation is the only thing being considered, because no further breeding will be done beyond that point.![]()