Last update: November 19, 2010 08:58:12 AM E-mail Print

 

Towards developing an economic efficiency index for dairy cattle in South Africa

 

M.J. Herselman1 , C.J.C. Muller2, S.W.P. Cloete2 , J.J. Olivier3 and  J. du Toit3


1Grootfontein ADI, P/Bag X529, Middelburg (EC), 5900; 

2Institute for Animal Production, Private Bag X1, Elsenburg, 7607;

3ARC LBD (Animal Production), Private Bag X5013, Stellenbosch, 7599

Corresponding author:  Tino Herselman

 


Selelection of dairy cows on a few production parameters has reduced the fertility of dairy cows, thereby reducing economic efficiency. An index-based selection approach, which also includes biological efficiency traits should be developed to overcome this problem. In New Zealand,  Breeding Worth, an index combining a linear combination of economic weights for lactation milk, fat and protein yield, mature cow live weight, longevity and fertility, is being used. For this paper, net income (Rand/cow/year) was used as a measure of economic efficiency. A profit equation was formulated by developing a simulation model for dairy cattle farming. This equation describes the change in net economic return as a function of a series of physical, biological and economic parameters. The profit function was subsequently used to define the selection goal as an objective function of different traits, each with its own discounted economic value. The following equation was derived:

 

Economic efficiency (R/cow/year) =  296 Yield + 34 Persistency – 1.69 BW + 581 Fat + 930 Protein - 2.33 Fertility + 195 Productive life, where

 

Yield:

EBV for milk yield (MY) at 60 days in milk (DIM) (l/day)

Persistency:

EBV for MY at 240 DIM/MY at 60 DIM (%)

BW:

EBV for body weight for mature cows (kg)

Fat:

EBV for milk fat % at the 60 DIM test (%)

Protein:

EBV for milk protein % at the 60 DIM test (%)

Fertility:

EBV for number of days from calving to first AI (days)

Productive life:

EBV for cumulative milk production period (months).

 

The genetic merit of a specific individual for economic efficiency is the sum of its genotypes for the different traits, each genotype being weighted by their predicted contribution to economic efficiency. Several aspects of the economic efficiency index-based selection need further refinement/investigation before implementation in industry, i.e., (i) reproduction data are currently not being recorded for genetic evaluation, (ii) the practicality of recording body weights for cows and (iii) the incorporation of condition score with body weight.