Effects of selection index coefficients that ignore reliability on economic weights and selection responses during practical selection

• Published in: Animal bioscience Vol. 31; no. 1; pp. 19 - 25
• Main Authors: Togashi, Kenji, Adachi, Kazunori, Yasumori, Takanori, Kurogi, Kazuhito, Nozaki, Takayoshi, Onogi, Akio, Atagi, Yamato, Takahashi, Tsutomu
• Format: Journal Article
• Language: English
• Published: Korea (South) Asian - Australasian Association of Animal Production Societies 01.01.2018; Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST); Asian-Australasian Association of Animal Production Societies; 아세아·태평양축산학회
• Subjects: Animal breeding; Cattle; Economic Weight; Genetic aspects; Quantitative Genetics; Selection Index; Selection Responses; 축산학; Selection Index; Economic Weight; Cattle; Quantitative Genetics; Selection Responses
• DOI: 10.5713/ajas.16.0991
• ISSN: 1011-2367; 2765-0189

In practical breeding, selection is often performed by ignoring the accuracy of evaluations and applying economic weights directly to the selection index coefficients of genetically standardized traits. The denominator of the standardized component trait of estimated genetic evaluations in practical selection varies with its reliability. Whereas theoretical methods for calculating the selection index coefficients of genetically standardized traits account for this variation, practical selection ignores reliability and assumes that it is equal to unity for each trait. The purpose of this study was to clarify the effects of ignoring the accuracy of the standardized component trait in selection criteria on selection responses and economic weights in retrospect. Theoretical methods were presented accounting for reliability of estimated genetic evaluations for the selection index composed of genetically standardized traits. Selection responses and economic weights in retrospect resulting from practical selection were greater than those resulting from theoretical selection accounting for reliability when the accuracy of the estimated breeding value (EBV) or genomically enhanced breeding value (GEBV) was lower than those of the other traits in the index, but the opposite occurred when the accuracy of the EBV or GEBV was greater than those of the other traits. This trend was more conspicuous for traits with low economic weights than for those with high weights. Failure of the practical index to account for reliability yielded economic weights in retrospect that differed from those obtained with the theoretical index. Our results indicated that practical indices that ignore reliability delay genetic improvement. Therefore, selection practices need to account for reliability, especially when the reliabilities of the traits included in the index vary widely.