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Proposed Plan for Cooperative Study of the Inheritance of Milk Composition

Department of Dairy, Michigan State University, East Lansing

ABSTRACT

Experiments concerning the inheritance of economic factors not previously studied extensively involve essentially the same pattern of procedure; namely, environmental factors which affect characters, adjustments which should be made, and the genetic parameters which can be estimated.

I. General considerations

Environmental factors affecting milk composition:

Age at calving

Stage and length of lactation

Month of calving

Breed

Calving interval, days dry, gestation period

Other factors: geographic and managemental effects, disease and other unusual circumstances.

Adjustments to be made. Using methods of least squares, one can measure and adjust for the effects found to be significant. These adjusted data then can be used to estimate the following genetic parameters:
Repeatability indicates the reliability of a single record as an indication of breeding value. If it is of sufficient magnitude, cows could be sampled for a single lactation or for periods during a lactation.