Studies On Genetic Evaluation Of Production Traits For Cattle With Test Day Model

The study were to apply to the first three lactation and monthly for milk,fat,protein and SCC for Holstein dairy cowsThe age model and the season model were used to absorbed the lactation curve for milk,fat,protein,fat percentage,protein percentage and SCS.From the age model,milk,fat,protein,fat percentage , protein percentage and SCS increased with age adding,but fat and protein yield decreased slowly with milk in days,except the first lactation peaked at approximately 80 MID;SCS increased with age and reached its lowest point at approximately the same DIM as peak milk yield,raised after that;SCS in multiparous cows were more than primiparous cows;From the season curve showed :winter calving cows productde more than those calving in summer,but slightly.The study concluded maths model of the first three lactation.TDM with RRM was used to estimated EBV for various partial lactation and persistency of the first lactation Holsteins and the genetic evaluation for individual,it showed:individuai differences in the shape of the genetic lactation curvesof cows.lt concluded maths model of milk,fat and protein yield.EBV correlations with various partial lactation and persistency showed :P₁ P₂ P₃ can all used to select the shape of lactation curve,and P₁ was the best.RRM can be based on different number of test day records and makes full ues of information to estimate breeding values,Based on EBV of persistency lactation curve could be modified genetically in test day model,and on EBV of various partial lactation improve accuracy of genetic evaluationand selection.