Author
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Wiggans, George |
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Hubbard, Suzanne |
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Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/3/2001 Publication Date: N/A Citation: N/A Interpretive Summary: To provide the dairy goat industry with accurate information for making breeding decisions, genetic evaluations of U.S. dairy goats are computed annually by USDA from records available through Dairy Herd Improvement programs and the American Dairy Goat Association (ADGA). For evaluation of yield traits, a statistical model similar to that used for dairy cattle is used, but lactation records are edited within limits appropriate for goats. Evaluations are computed for milk, fat, and protein yields and component percentages; an economic index based on genetic merit for milk, fat, and protein yields is calculated based on economic values for dairy cattle. A multitrait statistical model is applied for conformation traits. Annual genetic progress for does that were born during 1996 as a percentage of average breed yield was lowest for Toggenburgs (-.1%/yr, milk; .0%/yr, fat and protein) and highest for Saanens (.9%/yr, milk and protein; 1.0%/yr, fat). Annual genetic trend for type traits across breeds for does born during 1996 ranged from .67 for stature to -.12 for rear udder height. Two production-type indexes are computed by ADGA with 2:1 and 1:2 weightings for yield (represented by genetic merit for fat- corrected milk) and conformation (represented by genetic merit for final score). Evaluation release to the dairy goat industry is during July for yield and during November for conformation. Evaluations are available to producers through ADGA or a USDA web site. Greater rates of genetic improvement are likely if the economics of goat milk production improve. Because of the large number of progeny possible for an individual buck, especially because of artificial insemination and the short generation interval, genetic improvement could be rapid. Technical Abstract: Genetic evaluations of U.S. dairy goats are computed annually by USDA from records available through Dairy Herd Improvement programs and the American Dairy Goat Association (ADGA). 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 years. 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 6 parities of does born since July 1973 and kidded since January 1976 are edited within limits appropriate for goats, projected to 305 days, 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 protein yields 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 transformation. Annual genetic progress for does that were born during 1996 as a percentage of mean breed yield was lowest for Toggenburgs (-.1%/yr, milk; .0%/yr, fat and protein) and highest for Saanens (.9%/yr, milk and protein; 1.0%/yr, fat). Annual genetic trend for type traits across breeds for does born during 1996 ranged from .67 for stature to -.12 for rear udder height. Two production-type indexes are computed by ADGA with 2:1 and 1:2 weightings for yield (represented by genetic merit for fat-corrected milk) and type (represented by genetic merit for final score). |
