Genetic Evaluation of Yield and Type Traits of Dairy Goats in the United States

Abstract

Genetic evaluations of US dairy goats are calculated an-nually by USDA from records that are available through Dairy Herd Improvement programs and the American Dairy Goat Association (ADGA). The number of does in test plans used in genetic evaluations was 11,273 during 1999; participation in linear appraisal programs during 1999 was 3784 does, a decrease from the mean of 4285 does over the last 5 yr. For evaluation of yield traits, an animal model similar to that used for dairy cattle is used, but analysis is across breeds. Lactation records for the first six parities of does that were born since July 1973 and kidded since January 1976 are edited within limits appropriate for goats, projected to 305 d, and adjusted for kidding age and month. Evaluations are computed for milk, fat, and protein yields and component percentages; an economic index based on genetic merit for milk, fat, and pro-tein yields (MFP$) is calculated, based on economic values for dairy cattle. A multitrait animal model is applied to 13 linear type traits and final score. A single-trait calculation method is accomplished by applying a canonical transforma-tion. Annual genetic progress for does born during 1996 as a percentage of mean breed yield was lowest for Toggenburgs (–0.1%/yr, milk; 0.0%/yr, fat and protein) and highest for Saanens (0.9%/yr, milk and protein; 1.0%/yr, fat). Annual genetic trend for type traits across breeds for does born during 1996 was 0.67 for stature; 0.37 for rump angle; 0.34 for teat placement; 0.22 for suspensory ligament; 0.20 for strength; 0.16 for teat diameter; 0.12 for rump width; 0.09 for rear legs; 0.06 for dairyness; 0.05 for final score; 0.01 for fore udder attachment and udder depth; –0.1 for udder depth; and –0.12 for rear udder height. Two production-type indexes are com-puted by ADGA with 2:1 and 1:2 weightings for yield (repre-sented by genetic merit for fat-corrected milk) and type (repre-sented by genetic merit for final score).