Breed Composition Codes for Crossbred Dairy Cattle in the United States

John B. Cole,* Melvin E. Tooker, Paul M. VanRaden, and Joel H. Megonigal, Jr. Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350.

FOUR-GENERATION BREED STACKS

The four-generation breed stack is a text string describing an animal's breed

composition for the four most recent generations. This allows for the easy

identification of rotational crossbreeding systems. The breed stack for a HO x

GU F1 cow is:

Breed Composition------------------------------------------------------------HOGUHOHOGUGUHOHOHOHOGUGUGUGUHOHOHOHOHOHOHOHOGUGUGUGUGUGUGUGU

In this example, the sire and the dam are purebred animals for the previous four

generations.

INTRODUCTION

Crossbreds are animals whose genes are derived from more than one

breed, such as a cow with a Holstein sire and a Jersey dam. A system for

storing breed composition data for US dairy cattle has been developed and the

necessary software implemented. This system is necessary to facilitate

implementation of an across-breed genetic evaluation. Crossbred animals in the

US dairy cattle population do not currently receive genetic evaluations. Two

ways that crossbred animals may be handled in an evaluation are: they may be

included in the breed-of-sire evaluation, or all animals may be combined into a

single evaluation. For each crossbred cow (n=246,218) the database stores

animal identification, breed of animal registry, breed fractions for 18 dairy breeds

and an “unknown” category, a four-generation breed stack, a sire breed stack,

and a heterosis value. Standard two-letter breed codes are used in the breed

stacks. Breed fractions were calculated from pedigree information in the USDA

database as far back as data were available.

SUMMARY STATISTICS

There are currently 246,218 crossbred animals stored in the AIPL database.

Results are presented for the six major dairy breeds in the US: Ayrshire (AY),

Brown Swiss (BS), Guernsey (GU), Holstein (HO), Jersey (JE), Milking Shorthorn

(MS). The number of animals in the table with non-zero breed fractions are

presented in Table 1. The number of F1 animals for each of the six major breeds

are presented in Table 2.

SIRE BREED STACKS

The sire breed stack is a summary of the breed of sire and sires of the

maternal line as far back as pedigree data are available. The sire breed stack for

the HO x GU F1 from the previous example is:

Sire Breed Stack------------------------------------------------------------HOGUGUGUGU

Due to the absence of breed information about paternal ancestors, rotational

crossbreeding systems cannot be identified from the sire breed stack. However,

when purebred sires are used this information provides a complete description of

the mating system being used.

GENETIC EVALUATION OF CROSSBREDS

There are three basic approaches to using records from crossbred animals

in a genetic evaluation program:

• Do not use the records (the current system).

• Use the crossbred animals in the breed-of-sire evaluation.

• Use records from all animals in a single across-breed evaluation.

The current system, under which crossbred records are not used, is the least

desirable option because it discards information in the form of records. The third

option is the most technically challenging but appealing option. The second

option is not as satisfying as the third, but it is the simplest to implement.

CONCLUSION

There is now a system in place for easily identifying crossbred dairy cattle in

the United States, and research into methods for genetic evaluation of these

animals is ongoing.

Table 2. Number of F1s for each major breed cross.

Table 1. Number of animals with a non-zero breedfraction for each major breed.

AY BS GU HO JE MS0

20000

40000

60000

80000

100000

120000

140000

160000

11234

27030 29331

148539

50278

5571

Breed

Nu

mb

er

of

An

ima

ls

Breed AY BS GU HO JE MSAY 8,200 543 420 6,227 543 206BS 17,973 676 15,257 1,321 106GU 15,711 13,089 1,230 155HO 68,382 28,969 3,300JE 32,404 175MS 4,102