Inverse Numerator Relationship Matrix Approximation

Genetic evaluation by BLUP requires knowledge of the inverse numerator relationship matrix among breeding values. When pedigree information is complete, the true relationship matrix can be determined and an exact inverse found. When pedigree information is incomplete, an exact inverse of an approximate relationship matrix is obtainable. The usual algorithm for the inverse numerator relationship matrix may be derived assuming each unidentified parent to be a different base population animal.