Jersey is the second largest dairy breed in the USA. Originally from the Isle of Jersey, the first Jersey cows were brought to the U.S. in 1657. Jerseys are known for their high milk fat percentage, good calving ease and high heat tolerance. The breed has gained popularity as an efficient and sustainable dairy breed, with high cheese yield from smaller cows. Jerseys currently make up more than 10% of the U.S. dairy cow population.

Photo Courtesy of AJCA

The Jersey breed is represented by the American Jersey Cattle Association.

Learn about Jersey association activities, programs and services

National Production Averages

The average annual milk production for U.S. Holstein cows is well-documented by NDHIA through milk recording.

Genetic Conditions

Seven genetic abnormalities caused by recessive genes have been observed in Jerseys. Four lethal haplotypes have also been identified in Jerseys.

Genomic Testing

The American Jersey Cattle Association encourages genomic testing to measure animals’ true genetic merit.

Total Merit Index: JPI

Jerseys are ranked on the Jersey Performance Index (JPI). Traits included in this index are:

  • Protein
  • Fat
  • Milk Density
  • Productive Life
  • Livability
  • Somatic Cell Score
  • Daughter Pregnancy Rate
  • Cow Conception Rate
  • Heifer Conception Rate
  • Functional Trait Index
  • Health trait Index 

The functional trait index is comprised of the Jersey Udder Index (JUI) and several type traits. JUI is a Jersey Specific Udder index that can be compared to Udder Composite.

Generation Count Suffix

Official registered names of U.S. Jersey animals have a suffix consisting of a number inside curly brackets. This number represents the animals’ generation count. 

The Jersey generation count system was developed to embrace and label Jersey animals without fully known ancestry and to track Jerseys that have other breeds present in their pedigree. The generation count indicates where in the animal’s pedigree an ancestor exists that is unknown or of a different dairy breed. When the suffix is {1}, the animal will have one registered Jersey parent and one parent that is unknown or of a different breed. When this animal is bred to another registered Jersey, the name of the offspring would be marked by {2} as it is known that a grandparent is not a known registered Jersey. 

When an animal obtains suffix {6}, it is considered a purebred Jersey and the suffix is removed from the registered name. By then, any unknown or non-Jersey ancestor is 6 generations removed from the animal.  

Jersey bulls can be officially registered when their generation count is {4} or higher, with the stipulation that the bull is genotyped and has a Breed Base Representation of 100 and its sire and dam are also genotyped.