By Lawlor, T. J. and Rogers, G. W. and Short, T. H., Journal of Dairy Science, 1992
Description
Selection index was utilized to obtain index coeff. for milk yield and 7 composite type traits. Composite type traits were chosen to represent groups of highly correlated linear type traits (to reduce problems associated with correlated traits). The aggregate genotype (breeding goal) included milk yield, mastitis, milking labour, laminitis, ketosis and milk fever. Genetic parameters and economic values were based on literature values if available. Index coeff. for 15 linear type traits were calculated based on their heritabilities and the index coeff. for the representative composite type trait. Protein*3 + fat on a standardized basis was chosen to represent milk yield and was emphasized either 2, 3 or 4 times as much as the total for all 15 liner type traits in new equations. These new equations were used to calculate index values for the top 400 bulls based on the current Type-Production Index (TPI). These indexes ranked bulls differently when compared with the current TPI
Selection index was utilized to obtain index coeff. for milk yield and 7 composite type traits. Composite type traits were chosen to represent groups of highly correlated linear type traits (to reduce problems associated with correlated traits). The aggregate genotype (breeding goal) included milk yield, mastitis, milking labour, laminitis, ketosis and milk fever. Genetic parameters and economic values were based on literature values if available. Index coeff. for 15 linear type traits were calculated based on their heritabilities and the index coeff. for the representative composite type trait. Protein*3 + fat on a standardized basis was chosen to represent milk yield and was emphasized either 2, 3 or 4 times as much as the total for all 15 liner type traits in new equations. These new equations were used to calculate index values for the top 400 bulls based on the current Type-Production Index (TPI). These indexes ranked bulls differently when compared with the current TPI
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