Regression Tree Analysis of Factors Affecting First Lactation Milk Yield of Dairy Cattle

Abstract

The objective of this study was to examine the effects of management and environmental effects on first lactation milk yield by means of regression tree method. Regression tree method is useful to determine the effects of several factors on specified depended variables. The independent variables used in the model were factors such as farm, breed, year of calving, season of calving, age at calving and days in milk. Data used in this study were obtained from three state farms. The resulting data set consisted of 754 records from 1st farm, 1120 records from 2nd farm and 324 records from 3rd farm. The average total milk yield and days in milk were 5413.11 ± 2033.18 kg and 324 ± 64 days, respectively. Year of calving and days in milk were important variables affecting first lactation milk yield of dairy cattle, followed by farm and breed (p < 0.01). The determination coefficient of the prediction was found as 78.9%. As a result of the study 14 distinct paths from the root node to the leaves were presented.