Mathematical Models to Describe the Lactation Curves of Milk Trait of Iranian Holstein Dairy Cattle

The objective of this study was to compare the goodness of fit of lactation curve models; Wood, Wilmink, Linear Splines (SPL), Cubic Splines (SPC), Quadratic Splines (SPQ), Cobby and Le Du, Ali Schaeffer and Legendre Polynomial (LEG), in random regression model (RRM) for milk production traits of Iranian Holstein dairy cattle. For this purpose the records obtained from Test-day (TD) regarding milk (928513) yield related to their first parity were used. The estimated heritabilities by best models were lower in the beginning lactation than other during lactation (0.10 for milk yield. Additive genetic correlation between adjacent test days was more than between distant test days.