Breed Composition Codes for Crossbred Dairy Cattle in

Breed Composition Codes for Crossbred Dairy Cattle in the United States John B. Cole, * Melvin E. Tooker, Paul M. Van. Raden, and Joel H. Megonigal, Jr. Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705 -2350. INTRODUCTION Crossbreds are animals whose genes are derived from more than one breed, The sire breed stack is a summary of the breed of sire and sires of the maternal such as a cow with a Holstein sire and a Jersey dam. A system for storing breed line as far back as pedigree data are available. The sire breed stack for the HO x composition data for US dairy cattle has been developed and the necessary GU F 1 from the previous example is: software implemented. This system is necessary to facilitate implementation of Sire Breed Stack ------------------------------HOGUGU an across-breed genetic evaluation. Crossbred animals in the US dairy cattle population do not currently receive genetic evaluations. SIRE BREED STACKS Table 1. Number of animals with a non-zero breed fraction for each major breed. Two ways that Due to the absence of breed information about paternal ancestors, rotational crossbred animals may be handled in an evaluation are: they may be included in crossbreeding systems cannot be identified from the sire breed stack. However, the breed-of-sire evaluation, or all animals may be combined into a single when purebred sires are used this information provides a complete description of evaluation. For each crossbred cow (n=246, 218) the database stores animal Table 2. Number of F 1 s for each major breed cross. identification, breed of animal registry, breed fractions for 18 dairy breeds and an the mating system being used. GENETIC EVALUATION OF CROSSBREDS “unknown” category, a four-generation breed stack, a sire breed stack, and a There are three basic approaches to using records from crossbred animals in a heterosis value. Standard two-letter breed codes are used in the breed stacks. genetic evaluation program: Breed fractions were calculated from pedigree information in the USDA database • Do not use the records (the current system). as far back as data were available. • Use the crossbred animals in the breed-of-sire evaluation. SUMMARY STATISTICS FOUR-GENERATION BREED STACKS There are currently 246, 218 crossbred animals stored in the AIPL database. The four-generation breed stack is a text string describing an animal's breed Results are presented for the six major dairy breeds in the US: Ayrshire (AY), composition for the four most recent generations. This allows for the easy Brown Swiss (BS), Guernsey (GU), Holstein (HO), Jersey (JE), Milking Shorthorn identification of rotational crossbreeding systems. The breed stack for a HO x (MS). The number of animals in the table with non-zero breed fractions are GU F 1 cow is: presented in Table 1. The number of F 1 animals for each of the six major breeds are presented in Table 2. • 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 Breed Composition ------------------------------HOGUHOHOGUGUHOHOGUGUHOHOHOHOGUGUGUGU There is now a system in place for easily identifying crossbred dairy cattle in the In this example, the sire and the dam are purebred animals for the previous four United States, and research into methods for genetic evaluation of these animals generations. is ongoing.