Genetic Evaluation of Dairy Goats in the United States and Canada

Brian Sullivan, Canadian Centre for Swine Improvement
and
George Wiggans, United States Department of Agriculture

The United States Department of Agriculture calculates annual genetic evaluations of dairy goats from yield data collected through the Dairy Herd Improvement Program and from type and pedigree data supplied by the American Dairy Goat Association. Evaluations for milk, fat, and protein yields have been calculated since 1983 for bucks and since 1984 for does. An animal model replaced the sire model for yield in 1987. Evaluations for type have been calculated since 1986 for final score and since 1989 for linear type traits. In 1995, a multi‑trait animal model replaced the sire model for type. Evaluations are computed for Alpines, Experimentals, LaManchas, Nubians, Oberhaslis, Saanens, and Toggenburgs and for crossbred animals from these breeds. Only animals with registered sires are evaluated. The July 1999 milk, fat and protein evaluations included 205 011 does and 45 170 bucks, of which 9 333 bucks had at least 5 daughters, which is required for release of a buck evaluation to the industry. Evaluations for final score (type) in November 1998 included 62 243 does and 20 659 bucks, of which 1 804 bucks had at least 5 daughters. Records included start in 1976 for milk and 1988 for type. A selection index for yield traits is produced using the economic values derived for dairy cattle which is equal to 0.31 * PTA milk + 0.80 * PTA fat + 2.00 * PTA protein, where PTA is predicted transmitting ability. Two additional indices are also produced based on combinations of the above yield index and the PTA for final score. One has yield weighted twice as much as type, and the other has type weighted twice as much as yield.

Canadian dairy goats receive genetic evaluations annually for milk, fat and protein yield, and for body conformation (type) based on eight linear type traits. Both recording programs are managed by the Canadian Goat Society (CGS) which utilizes the services of provincial dairy cattle programs for milk recording, and Canadian Livestock Records Corporation for pedigree data. CGS also operates a milk recording option where groups of breeders test in each others herds. Milk records from all provinces are processed by the Quebec Dairy Herd Analysis Service. Genetic evaluations are computed by the Canadian Centre for Swine Improvement based on an animal model for both yield and type and have been available since 1991. The yield evaluations utilize an individual test day model developed at the University of Guelph. Evaluations are computed for Alpines, LaManchas, Nubians, Saanens and Toggenburgs, and include records on animals that have at least 3 generations of registered sires. The evaluations released in the Spring of 1999 included 62 018 individual test day records from 11 778 lactations on 6 636 does. The type evaluations were based on 5 452 first classification records. A total of 19 781 animals (including ancestors) were evaluated for yield, and 19 640 animals for type. Test day records start in 1987 and type records in 1981. Official yield evaluations are published for bucks with at least 5 daughter records, and type evaluations for bucks with at least 3 daughter records. A selection index for yield traits gives equal weight to milk and fat yield genetic evaluations. A type index gives 35% weight to 4 mammary system traits, 23% to general appearance, 15% to feet and legs, 15% to body capacity and 12% to dairy character. A third index combines the above yield and type indices with 60% weight on yield and 40% on type.