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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #141291

Title: ESTIMATE OF HERITABILITY AND GENETIC CHANGE FOR SURVIVAL OF HEREFORD COWS

Author
item MARTINEZ, GONZALO - UNIV. OF NEBRASKA-LINCOLN
item KOCH, ROBERT - RETIRED-UNIV. OF NEBRASKA
item Cundiff, Larry
item GREGORY, KEITH - ARS COLLABORATOR
item KACHMAN, STEPHEN - UNIV. OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2003
Publication Date: 7/1/2003
Citation: Martinez, G.E., Koch, R.M., Cundiff, L.V., Gregory, K.E., Kachman, S.D., Van Vleck, L.D. 2003. Estimate of heritability and genetic change for survival of hereford cows [abstract]. Journal of Animal Science Supplement 81(2):38.

Interpretive Summary: No interpretive summary is required.

Technical Abstract: Genetic parameters for survival measured in years between first calving and disposal were estimated using records for 2,053 Hereford cows born from 1964 to 1979 from a selection experiment with three lines selected for weaning weight (WWL), yearling weight (YWL), and an index of yearling weight and muscle score (IXL), and a control line (CTL). The model included year of birth as the only fixed factor and sire as the only random factor. The numerator relationship matrix accounted for all known relationships among sires. The survival analysis was carried out with a Weibull model with a penalized quasi-likelihood function. A record was considered censored if a cow was still alive at the end of the experiment or was sold or culled for reasons not related to the experiment. Genetic trends were estimated by regressing weighted means of estimated breeding values (EBV) of sires for years of birth of their daughters on birth year of the daughters. Environmental trends were estimated by regressing means of solutions for year of birth of the daughters on birth year. The estimate of the Weibull parameter was 1.30 (0.14), which indicates that the hazard for being culled increased with age. The overall median survival time was 5.2 years. The estimate of heritability (SE) for survival was: 0.06 (0.02) on the log scale and 0.15 when transformed to the original scale (years). Estimates of annual genetic change for survival were nearly zero for all lines. Selection of sires whose daughters are more likely to remain longer in the herd would be possible in a breeding program but could be relatively slow due to the low estimate of heritability. Comparison of changes in survival time for the selection and control lines showed that selection for weights at weaning and yearling ages had little effect on survival time in this experiment.