Optimum Model for Analyzing Lifetime Profitability of Holstein Cows

A A Shadparvar,S Nikbin

doi:10.5713/ajas.2008.70547

Abstract

This study was on the relative net income (RNI) for 18,286 Iranian Holstein cows from 799 herds, with first freshening between 1991 and 2000. Two kinds of production system, which differed mainly in milk pricing system and feed cost, were considered. Four different models adopted from the literature were examined to find the optimum model. They differed by the cost of rearing and growth after first calving and they needed different amounts of economic data at the farm level. Results showed that four measures of RNI were highly correlated (>0.96) and could be used equally to measure lifetime profitability of cows. Therefore, in herds without a regular system for recording economic and management data, use of the simplest model is recommended. Multiple regression analysis revealed that RNI was affected by age at first freshening, milk yield and days of productive life (DPL), regardless of production system, and a similar breeding goal could be defined for the two systems. Multiple regression analysis of RNI showed that in order to obtain an unbiased estimate of economic value for DPL, the per day milk yield, not total lifetime milk yield, should be included in the regression model along with DPL. Regression analysis suggested that it is possible to predict RNI using information on age at first freshening along with the length of first lactation and per day milk yield with a coefficient of determination ranging from 0.44 to 0.47.

Highlights

The economic merit of a dairy cow depends on profitable performance across a relatively long productive life
In Norman et al (1981), Relative Net Income (RNI) included milk income adjusted for average feed costs for production, value of each freshening reflecting average price of a calf adjusted for breeding costs and a salvage value
Additional costs were considered for growth from first freshening up to 42 months or disposal, feed costs and fixed and operating costs during days of productive life (DPL), and

Summary

Introduction

The economic merit of a dairy cow depends on profitable performance across a relatively long productive life. It can be measured by a profit function accounting for income and expense items over the cow’s lifetime (Balaine et al, 1981). Detailed economic data on lifetime performances of cows are rarely available to researchers. For the first time, Norman et al (1981) introduced the concept of Relative Net Income (RNI) which could be computed using data available from an ordinary dairy farm. In Norman et al (1981), RNI included milk income adjusted for average feed costs for production, value of each freshening reflecting average price of a calf adjusted for breeding costs and a salvage value. Additional costs were considered for growth from first freshening up to 42 months or disposal (whichever was first), feed costs and fixed and operating costs during days of productive life (DPL), and

Objectives

Discussion

Conclusion