National Genetic Evaluations | Individual Traits

Individual Traits

U.S. evaluations measure genetic variation for 50 unique traits important to dairy producers. Nearly all U.S. traits are calculated and published by the Council on Dairy Cattle Breeding (CDCB). Most U.S. traits are expressed as Predicted Transmitting Abilities, or PTAs, that measure the predicted difference of an animal’s offspring from the average population. In most cases, PTAs are expressed in the units used to measure the trait.

Selection indices combine many traits into a single value to rank animals, make selection decisions and optimize overall genetic progress. The U.S. national selection index is Net Merit.

Production and Yield

Milk Yield, Pounds
PTA Milk predicts the expected milk production of future mature daughters, in pounds, compared to other cows of the same breed born in the same base year

Fat Yield, Pounds
PTA Fat Pounds predicts the expected milk fat production of future mature daughters, in pounds, compared to other cows of the same breed born in the same base year

Fat Percent
Predicts the animal’s genetic ability to modify milk fat percentage. Expressed in percentage points above or below the breed base average

Protein Yield, Pounds
PTA Protein predicts the expected milk protein production of future mature daughters, in pounds, compared to other cows of the same breed born in the same base year

Protein Percent
Indicates the animal’s genetic ability to modify milk protein percentage. Expressed in percentage points above or below the breed base average

Feed Efficiency

Feed Saved (FSAV)
Indicates the expected reduction of consumed feed per lactation based on evaluations for residual feed intake and body weight composite. Measured in pounds of dry matter intake

Longevity & Health

Somatic Cell Score (SCS)
Indicates genetic susceptibility for udder health, as revealed through somatic cell count. Animals with PTA SCS <3.0 are expected to transmit improved udder health, and animals with PTA SCS >3.5 are expected to have daughters with cell counts higher than breed base average.

Productive Life (PL)
Predicts the time that female offspring are expected to remain in milking herd before removal by culling or death. Expressed as difference in months of productivity compared to breed base average

Cow Livability
Predicts the difference in female offspring expected to remain alive while in the milking herd, expressed in percentage points from the breed base average.

Heifer Livability
Predicts the difference in female offspring expected to remain alive between 2 days after birth and 18 months of age, expressed in percentage points from the breed base average.

Gestation Length (GL)
Expected influence the animal will have on the days that their female offspring carry their calves, expressed in days compared to breed base average

Displaced Abomasum (DA)
Expected resistance of an animal’s offspring to displaced abomasum, expressed in percentage points compared to breed base average

Hypocalcemia (MFEV)
Expected resistance of an animal’s offspring to milk fever, or hypocalcemia, expressed in percentage points compared to breed base average

Ketosis (KETO)
Expected resistance of an animal’s offspring to ketosis, expressed in percentage points compared to breed base average

Mastitis (MAST)
Expected resistance of an animal’s offspring to mastitis, expressed in percentage points compared to breed base average

Metritis (METR)
Expected resistance of an animal’s offspring to metritis, expressed in percentage points compared to breed base average

Retained Placenta (RETP)
Expected resistance of an animal’s offspring to retained placenta, expressed in percentage points compared to breed base average

Fertility and Calving

Sire Conception Rate (SCR)
Male fertility trait predicting future differences in conception rates of a service sire, expressed as a percent comparison deviated from the average of the breed’s A.I. bulls

Cow Conception Rate (CCR)
Female fertility trait predicting the lactating cow’s ability to conceive, defined as the percentage higher or lower likelihood to become pregnant at each service in comparison to the breed base average. A PTA CCR of 1 implies that daughters of this bull are 1% more likely to become pregnant during that lactation than daughters of a bull with an evaluation of 0

Heifer Conception Rate (HCR)
Female fertility trait predicting the maiden heifer’s ability to conceive, defined as the expectation the next insemination will produce a pregnancy in comparison to the breed base average. Expressed in percentage points compared to breed base average.

Daughter Pregnancy Rate (DPR)
Female fertility trait that predicts the percentage of non-pregnant cows that become pregnant during each 21-day period compared to breed base average

Sire Calving Ease (SCE)
Predicts the tendency of service sires to produce calves to be born more or less easily, expressed as percentage of difficult births in a first calving (primiparous heifers)

Daughter Calving Ease (DCE)
Predicts the ability of a service sire’s female offspring (daughter) to calve easier or more difficult, expressed as percentage of difficult births in a first calving

Service Sire Stillbirth (SSB)
Predicts the tendency of service sires to produce offspring that are stillborn (dead at birth or within 48 hours of birth), expressed in percentage points

Daughter Stillbirth (DSB)
Predicts the tendency of a service sire’s female offspring (daughter) to have offspring that are stillborn (dead at birth or within 48 hours of birth), expressed as percent of stillbirths

Early First Calving (EFC)
Indicates the animal’s genetic ability to alter the age of their female offspring at first calving, defined in days compared to the breed base average

Conformation and Type

PTA Type
Predicts the animal’s genetic ability to transmit to the offspring’s final classification or appraisal score in the breed’s classification program. Published by appropriate breed association

Udder Composite (UDC)
Index that combines several udder traits, weighted to reflect each trait’s contribution to higher udder scores. Published by appropriate breed association

Feet and Legs Composite (FLC)
Index that combines several feet and leg traits, weighting the traits by their economic benefit. Published by appropriate breed association

Body Weight Composite (BWC)
Index of body size (dimensions of the cow) and dairy form. Published by appropriate breed association

Linear Type Traits
The 18 linear type traits are expressed as Standard Transmitting Abilities (STAs) in the Holstein breed and as a percentage point deviation in the other breeds. Published by CDCB based on breed association type classification data.