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Title: Short Communication: Genetic and environmental relationships between milk yield and kidding interval in dairy goats

Author
item MONTALDO, H - Universidad Nacional Autonoma De Mexico
item VALENCIA-POSADAS, M - University Of Guanajuato
item Wiggans, George
item SHEPARD, L - American Dairy Goat Association
item TORRES-VAZQUEZ, J - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP)

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2009
Publication Date: 1/1/2010
Citation: Montaldo, H.H., Valencia-Posadas, M., Wiggans, G.R., Shepard, L., Torres-Vazquez, J.A. 2010. Short Communication: Genetic and environmental relationships between milk yield and kidding interval in dairy goats. Journal of Dairy Science. 93(1):370-372.

Interpretive Summary: Because of the great economic importance of fertility, reproduction traits have been incorporated as a selection criterion for dairy cattle in many countries. However, knowledge of those relationships in dairy goats is extremely limited, and estimation of heritabilities and correlations is needed. Genetic and environmental parameters for first-lactation milk yield and interval between first and second kidding were determined for Alpine, Nubian, Saanen, and Toggenburg dairy goats. Heritability was estimated to be 36% for first-lactation milk yield and 5% for first kidding interval. Increased milk yield was associated with longer kidding intervals both genetically and environmentally. The presence of unfavorable genetic and environmental relationships between milk yield and kidding interval indicates a need to include reproductive performance as a selection criterion and to develop feeding and other management strategies to optimize expression of both traits in dairy goat production systems. Fertility should be included as a selection criterion in dairy goat breeding programs to avoid its decline.

Technical Abstract: First-parity 305-day milk yield and intervals between first and second kiddings from 1975 through 2005 were analyzed to estimate genetic and environmental parameters for U.S. Alpine, Nubian, Saanen, and Toggenburg dairy goats. The complete data set included information from 5,180 sires, 23,827 does with data for first-parity milk yield, and 12,813 does with data for first kidding interval. Data were analyzed using average-information restricted maximum likelihood and bivariate mixed models within and across breeds. Fixed effects were month and herd-year of kidding within breed and month and breed-herd-year of kidding across breeds. Random effects were animal and residual. The heritability estimate for first-parity milk yield was 0.36 across breeds and ranged from 0.34 to 0.41 within breed; heritability for first kidding interval was 0.05 across breeds and ranged from 0.00 to 0.14 within breed. Genetic correlation between first-parity milk yield and first kidding interval was positive (unfavorable) across breeds (0.39); all environmental correlations within and across breeds were unfavorable (0.19 to 0.33). The presence of unfavorable genetic and environmental relationships between milk yield and kidding interval indicates a need to include reproductive performance as a selection criterion and to develop feeding and other management strategies to optimize expression of both traits in dairy goat production systems.