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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 #154353
Title: NUMBER OF CALVES BORN, NUMBER OF CALVES WEANED, AND CUMULATIVE WEANING WEIGHT AS MEASURES OF LIFETIME PRODUCTION FOR HEREFORD COWS

Author
item MARTINEZ, G. - ARAGUA, VENEZUELA
item KOCH, ROBERT - UNIV. OF NEBRASKA-LINCOLN
item Cundiff, Larry
item GREGORY, KEITH - ARS COLLABORATOR
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2004
Publication Date: 5/1/2004
Citation: Martinez, G.E., Koch, R.M., Cundiff, L.V., Gregory, K.E., Van Vleck, L.D. 2004. Number of calves born, number of calves weaned, and cumulative weaning weight as measures of lifetime production for Hereford cows. 82:1903-1911.

Interpretive Summary: Genetic parameters for lifetime production for cows with opportunity to live to 2 through 7 yr of age measured by number of calves born, number of calves weaned, and cumulative weaning weight, were estimated using data of 3,064 Hereford cows from a selection experiment with a control line and three lines selected for weaning weight, yearling weight, and an index of yearling weight and muscle score. The high estimates of genetic correlations among opportunity groups within the measures of lifetime production indicate that cumulative records through as early as 2 years of age would predict subsequent cumulative records through 7 years of age with reasonable accuracy, i.e., prediction can be made early in a cow's life. The moderate to high estimates of genetic correlations across the three measures of lifetime production indicate that cumulative records through 2 years of age predict subsequent cumulative records through 7 years of age with reasonable accuracy. The negligible estimates of genetic change for any of the measures of lifetime production indicate that successful selection of the lines for weights at relatively young weaning or yearling ages had little impact on lifetime reproduction. Increases in genetic values for measures of cumulative weight of calves weaned by a cow reflect effectiveness of selection for weaning and yearling weights in the selection lines.

Technical Abstract: Genetic parameters for lifetime production for cows with opportunity to live to 2 through 7 yr of age measured by number of calves born (NB), number of calves weaned (NW), and cumulative weaning weight (CW), were estimated using data of 3,064 Hereford cows from a selection experiment with a control line (CTL) and three lines selected for weaning weight (WWL), yearling weight (YWL), and an index of yearling weight and muscle score (IXL). Weaning weights were adjusted to 200 days of age and for sex and age of dam. Estimates of heritability and genetic and environmental correlations were obtained by REML with bivariate animal models with year of birth of the cow as a fixed effect and direct genetic and residual as random effects. Genetic trends were estimated by regressing means of estimated breeding values by year of birth and line on birth year. Estimates of heritability (SE) for opportunity groups of 2 to 7 years of age, ranged from 0.08 (0.03) to 0.16 (0.05) for NB; from 0.05 (0.02) to 0.16 (0.05) for NW; and from 0.06 (0.02) to 0.16 (0.05) for CW. Estimates of genetic correlations (SE) among NB traits ranged from 0.60 (0.14) to 1.00 (0.00), and estimates of environmental correlations (SE) ranged from 0.67 (0.02) to 0.99 (0.00). For NW, estimates of genetic and environmental correlations ranged from 0.98 (0.11) to 1.00 (0.00) and from 0.65 (0.02) to 0.99 (0.00), respectively. Estimates of genetic correlations (SE) among CW traits ranged from 0.94 (0.08) to 1.00 (0.00). Estimates of environmental correlations (SE) ranged from 0.66 (0.02) to 0.99 (0.00). Estimates of genetic correlations for NB through 2 yr of age (NB2) with all definitions of NW from 2 through 7 yr of age (NW2...NW7) ranged from 0.47 (0.18) to 0.71 (0.12) and with all definitions of CW ranged from 0.55 (0.16) to 0.80 (0.11). Estimates of genetic correlations between NW2 and all definitions for CW ranged from 0.95 (0.02) to 0.99 (0.06). Estimates of annual genetic (SE) change were negligible for NB2, NB6, NW2, and NW7 for all lines. Estimates of annual genetic (SE) change for CW2 were 0.85 (0.11), 0.79 (0.14), 0.51 (0.10), and 0.52 (0.18) kg/yr and for CW6 were 5.01 (1.25), 2.64 (1.75), 3.67 (1.16), and 3.33 (2.37) kg/yr for WWL, YWL, IXL, and CTL, respectively. Selection for lifetime production as measured by NB, NW or CW could be effective but would be relatively slow due to low estimates of heritability and to increased generation intervals.