Breeding terms explained in a nutshell

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BREEDING TERMS EXPLAINED IN A NUTSHELL Japie van der Westhuizen

Unbiased Prediction) methodologies to ensure that the prediction is independent of selection or mating bias. In these predictions, BLUP (multiple trait animal model) makes use of four sources of information, namely:

• Pedigrees (indication, on average, what proportion of “additive genes” are shared as relationships among all animals in the very simple definition for a Breeding pedigree, included in the evaluation). Value could be: • Actual (phenotypic) recordings among animals subjected to the same “The genetic value of an animal as a parent environmental (and management) for a specific trait (or group of traits)”. conditions (group) that contribute to This immediately means that such a value average performance. must be compared to a standard or a • The proportion of the differences in benchmark. Normal benchmarks are performance among the animals due to their comparisons with: genetic merit or, differently put, their • Other animals’ breeding values (usually breeding value differences, in relation to those also considered as selection the total differences in performance of all candidates). the animals in the same environmental (and management) condition (group). This is • The average breeding value of a called the heritability of the trait. population or group of other animals (like those in the same breed, born in the same • The proportion of differences in breeding country, born in a specific year (the sovalues for different traits influenced by the called “base year”) or even the average of same portions of the genome (the collective animals in a of all genetic code). herd). This is called the BLUP breeding values based on the animal model used to genetic correlation be known as the Rolls Royce of breeding value predictions. A breeding value is Current practices, namely gBLUP (genomic BLUP) using among different traits. therefore “population the single step in a comprehensive multiple trait animal dependant” (the The accuracy of model, that also accounts for heterogeneous variances, comparison of its predicting a “true” additional random effects, gaps in pedigrees, non-additive progeny relative to gene action and complex interactions is evidence of the breeding value depends progress to accurately predict the true genetic merit for the progeny of others on the information used production animals that must perform in such predictions, under the same basically the accuracy conditions or in the and completeness of same population). pedigree information and the proportion of animals …

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