A mixed-breed dog (also called a mutt or mongrel) is a dog that is a mixture of two or more breeds. Mixed-breed dogs vary in size, shape, and color, making them hard to classify physically, but some colors are more common than others. With each generation of mixing, the offspring move closer to the genetic norm. Dogs that are descended from many generations of mixes are typically light brown or black and weigh about 18 kg (40 lbs). The theory of hybrid vigor suggests that dogs of mixed ancestry will be healthier than their purebred counterparts. In some cases this might be true, because inbreeding among purebreds has made some breeds prone to various genetic health problems. Historically, dog shows and dog sports excluded mixed-breed dogs from competition. While this tradition is changing, some sports still remain open only to one breed of dog, such as greyhound racing. (more...)
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