The lifetime merit indices promote a balance of traits to maximize dairy cow profitability. These CDCB indices estimate the difference in lifetime profit that each animal is expected to transmit to its progeny, expressed in U.S. dollars.
Indices are valuable tools in cattle breeding because they combine many traits into a single value that drives genetic progress, ranks animals and streamlines management decisions. Net Merit accounts for more than 40 traits – including production yield, conformation, health and fitness, fertility and feed intake. Some traits are represented through composites, such as calving ability, health dollars, udder, feet and legs, and body weight.
When a trait has both economic value and genetic variation, including it in the lifetime merit indices increases profitability for dairy herds using the index.
Traits are weighted based on their genetic impact on farm profitability.
The lifetime merit indices are updated periodically to reflect new traits, new research and current dairy market data. The August 2021 revision was significant with three new CDCB traits incorporated – Early First Calving, Heifer Livability and Feed Saved. Emphasis shifted toward longer Productive Life and smaller Body Weight Composite. The 2021 formula more accurately reflects differences in production costs between cows, as new feed efficiency research showed cows’ actual maintenance costs are higher than previously estimated.
Net Merit was introduced in 1994 by renowned USDA geneticists who continue to conduct research that modernizes the U.S. genetic evaluations.
CDCB publishes 4 lifetime merit indices that are similarly expressed but differ in the emphases assigned to individual traits. Net Merit fits the milk market and management system for many U.S. dairy herds. Cheese Merit, Fluid Merit and Grazing Merit estimate profit potential in specific milk markets and grazing herds.
Lifetime Cheese Merit $ (LCM$) is designed for herds that produce milk for cheese, using cheese yield pricing. Cheese Merit factors in the same traits as Net Merit, but Cheese Merit assigns a negative economic weight on PTA Milk and places more emphasis on Protein Pounds, because protein has more value in the cheese market. Low somatic cell score is prized in this index as high SCS decreases cheese yield in the milk.
Lifetime Fluid Merit $ (LFM$) fits farms that sell into the fluid milk market. While Fluid Merit combines the same traits as Net Merit, there is considerably more weight on PTA Milk. Protein has no influence in Fluid Merit, as there is little (if any) payment for protein in fluid markets.
Lifetime Grazing Merit $ (LGM$) was created for pasture-based herds using intensive grazing. Relevant economic values and trait weightings reflect this herd management. As grazing herds often calve seasonally, fertility receives more emphasis (2.5 times more) “than in the other three indices.” Production yield, longevity, livability and udder health also differ. Read more in this published paper.
By breed, the formulas for lifetime merit indices differs slightly, because some U.S. traits are not available for all breeds. For Holsteins, evaluations are published for all major U.S. traits. The traits for feed intake, health, heifer livability, stillbirth, and calving ease are not evaluated in all breeds. Breed differences are described in this 2021 USDA paper.
Most U.S. breed associations have developed customized indices that align with goals set by the breeders, such as Total Performance Index (TPI™) in Holsteins and Jersey Performance Index (JPI).
Genetic indexes are updated periodically to add traits, incorporate new research and reflect current economics.
First national composite genetic index published by USDA
Composite indices that combined milk traits and type available
Lifetime merit indices introduced by USDA, accounting for income and cost in production, fitness and conformation traits. This blend was unique from indexes in most countries.
Addition of Udder Composite, Feet and Legs Composite and Body Weight Composite
Daughter Pregnancy Rate added
Calving traits considered through sub-index
Heifer and Cow Conception Rate added
Cow Livability incorporated
Disease resistance through health trait sub-index
Addition of Residual Feed Intake, Heifer Livability, Early First Calving
