IMPROVING GENETIC PREDICTIONS FOR DAIRY ANIMALS USING PHENOTYPIC AND GENOMIC INFORMATION
Title: Breed differences over time and heritability estimates for production and reproduction traits of dairy goats in the United States
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2012
Publication Date: May 1, 2012
Citation: Garcia-Peniche, T.B., Montaldo, H.H., Valencia-Posadas, M., Wiggans, G.R., Hubbard, S.M., Torres-Vazquez, J.A., Shepard, L. 2012. Breed differences over time and heritability estimates for production and reproduction traits of dairy goats in the United States. Journal of Dairy Science. 95(5):2707-2717.
Interpretive Summary: Knowledge of breed characteristics and genetic parameters for economically important traits of dairy goats are major factors in improvement of productivity and development of breeding programs as well as in identification of genetic resources. However, comprehensive studies of differences among U.S. dairy goat breeds for production and reproduction traits and their genetic parameters were limited and often not current. Milk production and reproduction traits of U.S. dairy goats were characterized based on kiddings from 1976 through 2005. Saanens had the highest milk and protein yields; Nubians had the highest fat yields. Nubians, Alpines, and Saanens had the highest combined fat and protein yields. Saanens were oldest at first kidding. Kidding intervals were shortest for Oberhaslis, LaManchas, and Nubians. Heritability estimates were 5% for kidding interval, 23% for age at first kidding, 35 to 37% for yield traits, and 52 and 54% for fat and protein percentages, respectively. Selection can be successful within breed for production and reproduction traits.
Differences over time among US dairy goat breeds were documented for production and reproduction traits; heritabilities and repeatabilities were estimated. Data were from herds with 2 breeds or more (Alpine, LaMancha, Nubian, Oberhasli, Saanen, or Toggenburg). Three kidding periods were examined: 1976 through 1984, 1985 through 1994, and 1995 through 2005. Repeatability mixed models were used to analyze milk, fat, and protein yields, combined fat and protein yield, fat and protein percentages, protein:fat ratio, age at first kidding, and kidding interval. Trends were favorable for most yield traits across time for all breeds but generally unfavorable for reproduction traits. Saanens had the highest milk (1,063 to 1,125 kg) and protein yields (31 to 33 kg) across time; Nubians had the highest fat yields (37 to 40 kg). Nubians had the lowest milk yields (791 to 851 kg); Oberhaslis had the lowest fat (31 to 33 kg) and protein (23 to 27 kg) yields. Alpines had the largest increase in milk (7.4%) and fat (8.8%) yields across time; Oberhaslis had the largest increase in protein (17.4%) and combined fat and protein (13.2%) yields. Combined fat and protein yield was higher for Nubians, Saanens, and Alpines (65 to 72 kg) and lower for LaManchas, Toggenburgs, and Oberhaslis (53 to 67 kg). Nubians had the highest fat (4.7 to 4.8%) and protein (3.6 to 3.8%) percentages. Only Nubians increased in fat percentage (2.1%) over time; protein percentage increased most for Toggenburgs (7.4%) and Alpines (7.1%). Protein:fat ratio was highest for Toggenburgs (0.84 to 0.89) and lowest for Nubians (0.76 to 0.81), but Nubians had the largest increase in protein:fat ratio over time (6.6%). Saanens were oldest at first kidding (509 to 589 days), and Toggenburgs and LaManchas generally were youngest (435 to 545 days); age at first kidding increased most for Alpines (21.8%) and LaManchas (21.6%). Kidding intervals generally were shorter for Oberhaslis, LaManchas, and Nubians (350 to 377 days) than for Toggenburgs, Alpines, and Saanens (373 to 387 days). Kidding interval increased most for Nubians (3.9%) and Saanens (3.8%); kidding interval decreased over time only for Oberhaslis (5.4%). Heritability estimates across breeds were 0.35 for milk and fat yields, 0.37 for protein yield, 0.52 for fat percentage, 0.54 for protein percentage, 0.23 for age at first kidding, and 0.05 for kidding interval. Genetic selection within breed is feasible for production and reproduction traits of US dairy goats.