Animal BLUP

Heritability is a population parameter describing the proportion of phenotypic variance due to additive genetic effects (0-1 scale). BLUP is a prediction method that uses heritability as an input to estimate an individual animal's breeding value. High heritability means BLUP predictions are more accurate; low heritability means environmental variation dominates and predictions are less precise. They are complementary concepts.

Yes. BLUP predicts breeding values for all animals, regardless of whether they have records. A young animal's initial BLUP is based entirely on its parents' and relatives' records. As the animal accumulates its own performance data (or offspring performance), its BLUP is updated and becomes more accurate.

Pedigree errors (e.g., incorrect parentage) bias predictions for the misidentified animal and its relatives. The bias propagates through multiple generations because BLUP relies on pedigree relationships to borrow information. Even small pedigree errors can accumulate and distort breeding decisions across many animals.

Yes, BLUP explicitly partitions observed performance into fixed environmental effects and random genetic effects. Environmental effects (e.g., herd, year, season) are estimated and removed from records before calculating breeding values. However, gene-by-environment interactions (where an animal's genetic superiority differs across environments) are not modeled in standard BLUP.