Genetic evaluation of dairy cattle based on morning and afternoon milking test day records with fixed regression model

This study evaluated morning and afternoon test day records for genetic evaluation of dairy cattle.  The data were taken form 128,087 test day yield records for the first four lactations of Holstein cows from 2007 to 2017, from Nucleus Breeding Center of dairy cattle in Indonesia. The records consisted of morning and afternoon and total milk yields from 823 cows, resulting from 133 sires and 520 dams; records were restricted to Day Interval Milk (DIM) between 5 and 305 days production. The genetic parameters were estimated with REML by using animal model with fixed regression. Ali and Schaeffer has a good fit for morning, afternoon and total test day yields with the coefficient of determination ranging from 0.980 to 0.995. Estimates of heritability were 0.177, 0.220, and 0.213 for morning, afternoon, and total test day records, respectively.  Spearman rank correlations of breeding values between total yield and morning and afternoon yields, for both animals and sires, ranged between 0.953 and 0.968.  In conclusion, morning and afternoon yields can be used for genetic evaluation of dairy cattle. Key words: Genetic parameters, heritability, morning and afternoon yields, fixed regression model, dairy cattle.