Five possible matings with polled shetlands.

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These are the five matings possible when using a polled or half-polled shetland sheep, either ram or ewe. Courtesy of Dolling's "Breeding Merinos".     By preparing a genotype table of both parents, and the alleles they can pass down, we can easily see a predicted ratio of what offspring can be expected from these matings. Remember that which gene will pass down is a flip of the coin, each time. Chance deviations from these frequencies must be expected when we look at the result of actual matings.    Each table is reciprocal in that either the top or side can represent either the ram or the ewe. For the sake of clarity, the p' gene was not included, as it is likely that horned ewes would already have been eliminated in a polled flock, although it isn't necessary to do this in order to breed for polled rams.

Mating type #1: Full-poll (PP) to full-poll (PP).                                                           PP                                          P                         P                       ___________________________________                      P                PP                       PP PP                  ___________________________________                       P                PP                       PP      Both sire and dame produce gametes only containing P (poll). Only PP (full-poll) offspring may result from this type of mating. This type of breeding can only be expected in a flock that has been breeding for polled for a long time.

Mating type #2   Full-poll (PP) to horned (pp).                                                PP                                     P                       P                   __________________________________                     p              Pp                      Pp pp                   __________________________________                     p              Pp                      Pp     A full-poll ram or ewe is bred to a sheep carrying two horn genes. All of the offspring will be half-polls.

Mating type #3:  Half-poll (Pp) to horned (pp).                                                  Pp                                         P                    p                                        ________________________________________                                   p              Pp                  pp pp                         ________________________________________                        p              Pp                  pp   A half-poll ram or ewe is bred to a sheep carrying two horn genes. Half of the offspring will be half-polls, and half will be carry two horn genes.

Mating type #4: Half-poll (Pp) to half-poll (Pp).                                                     Pp                                    P                                p                      _________________________________________                          P        PP                              Pp Pp                       _________________________________________                         p         Pp                              pp     Two carriers bred together will have an expected ratio of producing 50% half-polls (Pp),  25% full-polled (PP), and 25% horned (pp).

Mating type #5: Full-poll (PP) mated to half-poll (Pp).                                              PP                                 P                               P                  __________________________________________                     P           PP                           PP Pp                               ___________________________________________                        p            Pp                           Pp      A full-poll bred to a half-poll has an expected ratio of 50% full-poll, and 50% half-poll.