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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 #171143
Title: GENETIC PARAMETERS FOR STAYABILITY, STAYABILITY AT CALVING AND STAYABILITY AT WEANING TO SPECIFIED AGES FOR HEREFORD COWS

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

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2005
Publication Date: 9/1/2005
Citation: Martinez, G.E., Koch, R.M., Cundiff, L.V., Gregory, K.E., Kachman, S.D., Van Vleck, L.D. 2005. Genetic parameters for stayability, stayability at calving and stayability at weaning to specified ages for Hereford cows. Journal of Animal Science 83:2033-2042.

Interpretive Summary: Stayability (time remaining in the herd after first calving as a 2-yr-old) was studied in three lines selected for weaning and yearling weights and a control line of Herefords. Estimates of heritability were large enough that selection for stayability could be effective although direct selection would be slowed by a long generation interval. Measures of stayability at early ages, however, were genetically correlated enough with measurements through eight years of age that the early measures could provide effective predictors of stayability through eight years of age which would shorten the generation interval. Calculation of genetic change for various measures of stayability showed essentially no change over the period of the selection experiment (cows born 1964 through 1979) for the selection lines or for the control line which shows that selection for growth may have little effect on stayability which is an important part of cow efficiency.

Technical Abstract: Genetic parameters for measures of stayability to six different specified ages (ST1,',ST6), for five measures of stayability to calving (SC2|1,',SC6|1), and for five measures of stayability to weaning (SW2|1,',SW6|1), were estimated using records of 2,019 Hereford cows collected from 1964 to 1979 from a selection experiment with three selected lines and a control line. The model included year of birth as a fixed effect and sire as a random effect. Analyses were performed with 1) a generalized linear mixed model for binary data using a probit link with a penalized quasi-likelihood function and 2) with a linear mixed model using REML. Genetic trends were estimated by regressing weighted means of estimated breeding values (EBV) of sires by yr of birth of their daughters on birth yr. Environmental trends were estimated by regressing means of solutions for yr of birth on birth yr. Estimates of heritability (SE) for ST were between 0.09 (0.08) and 0.30 (0.14) for threshold model and between 0.05 (0.04) and 0.19 (0.09) for linear model. Estimates of heritability from linear model analyses transformed to an underlying normal scale were between 0.09 and 0.35. Estimates of heritability (SE) for SC were between 0.29 (0.10) and 0.39 (0.11) and between 0.18 (0.09) and 0.25 (0.08) with threshold and linear models. Estimates of heritability transformed to an underlying normal scale were between 0.30 and 0.40. Estimates of heritability (SE) for SW were between 0.21 (0.14) and 0.47 (0.19); and 0.12 (0.08) and 0.26 (0.12) with threshold and linear models. Estimates of heritability transformed to an underlying normal scale were between 0.21 and 0.50. Estimates of genetic and environmental trends for all lines were nearly zero for all traits. Correlations between EBVs for sires for stayability at specific ages, for stayability at calving, and for stayability at weaning with threshold and linear models ranged from 0.09 to 0.82, from 0.68 to 0.90, and from 0.67 to 0.87, respectively. Selection for stayability would be possible in a breeding program and could be relatively effective due to the moderate estimates of heritability, which would allow selection of sires whose daughters are more likely to remain longer in the herd. Selection for increased weights at weaning and yearling ages resulted in little genetic change in stayability for any definition of stayability.