Tip of The Day - October 12, 2016

Photo by Tom Semadeni

Bee's work

1988 Selection on Milk Components

John Gibson

One objective was to see whether different methods of calculating economic weights had substantial effects on the economic response to index selection. Another was to examine the effect of different payment and quota systems on breeding objectives for milk components.

Responses to individual and sire selection on indexes of carrier (water), fat, protein, and lactose were examined for various sets of economic weights, population parameters and indexes omitting protein and lactose. Twenty one sets of economic weights represented several Canadian pricing structures, with methods of derivation including various costs and scaling to different end points. Population parameters were either literature averages or estimates for Holsteins in Canada, with several sets of assumed parameters for lactose yield.

Alternative economic weights led to reductions of economic responses of up to 41%. Use of literature values reduced responses by 14%, whilst use of different parameters for lactose reduced responses up to 8%. Generally, protein was slightly more important in the index than lactose, but in specific situations the reverse was true. Collection of data on lactose yield is probably not worthwhile when the genetic merit of selected animals is estimated with high accuracy, but might be worthwhile when accuracies are lower, such as in MOET nucleus schemes.

Photo by Tom Semadeni