Selection and cloning methods are disclosed that are effective for the
selective multiplication of desired animals, for instance livestock
animals. These methods can be used to expand populations of animals, and
are particularly useful for duplicating animals selected based on traits
that are measured after the animal is deceased. Certain embodiments
include techniques useful for selecting a desirable bovine animal (e.g.,
a desirable steer) based at least in part on a measurable carcass trait.
Also described are specific cloning techniques that involve repetitive
(for instance, two) cycles of cloning, such as nuclear transfer cloning.
In specific embodiments, a two-step cloning system is described, in which
the nuclear donor of the first cloning cycle is an adult fibroblast cell
and the nuclear donor of the second cloning cycle is a fetal fibroblast
harvested from a fetus that arose from the first cloning cycle.