Dairy farmers will have to recalibrate those genetic numbers they carry around in their heads as they select new sires come April. The reason: The genetic base on 102 traits will be adjusted to reflect genetic progress over the past five years.
The genetic base is updated every five year; cows born in 2015 will define the new base. “Because gains were made across five years for most traits, most of these Predicted Transmitting Abilities (PTAs) will be lowered (by the amount of the five-year gain),” say Duane Norman, Paul VanRaden and George Wiggans. Norman and Wiggans are Council on Dairy Cattle Breeding technical advisors; VanRaden is a USDA-Agricultural Research Service geneticist.
Of the traits analyzed, favorable gains were made for 81 while 18 were unfavorable. For example, all six breeds showed positive gains for Lifetime Net Merit: Ayrshire, +121; Brown Swiss, +60; Guernsey, +77, Holstein, +231; Jersey, 191, and Milking Shorthorn, +45.
In fact, gains were positive for all breeds for all Merit Indexes: Lifetime, as mentioned, Cheese, Fluid and Grazing. “Thus, the merit indexes for all breeds will be lowered in April,” say the geneticists.
But some traits did not improve. Fertility may be the most glaring, with 13 of the 18 fertility traits showing unfavorable changes since 2015. Holsteins were the only breed to show improvement in all three: Daughter pregnancy rate, +.24; heifer conception rate, +.50, and cow conception rate, +.38.
For more complete information on all the traits and how they will change in April, click here .