HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Martinez, G. E. Articles by Van Vleck, L. D. Search for Related Content PubMed PubMed Citation Articles by Martinez, G. E. Articles by Van Vleck, L. D.

Genetic parameters for six measures of length of productive life and three measures of lifetime production by 6 yr after first calving for Hereford cows¹

G. E. Martinez^*,2, R. M. Koch^*, L. V. Cundiff, K. E. Gregory and L. D. Van Vleck^,,3

^* Department of Animal Science, University of Nebraska, Lincoln 68583-0908; and ARS, USDA, Roman L. Hruska U.S. Meat Animal Research Center, and Clay Center, NE 68933 and and Lincoln, NE 68583-0908

³ Correspondence: A218 Animal Science (phone: 402-472-6010; fax: 402-472-6362; e-mail: lvanvleck{at}unlnotes.unl.edu).

Genetic parameters for length of productive life given the opportunity (LPL|O), measured as days between first calving and disposal conditioned on one of six opportunity groups, L1 through L6 (e.g., L2 is length of productive life in days given the opportunity to live 2 yr after first calving), and lifetime production (LP), measured as the number of calves born (NB), number of calves weaned (NW), and cumulative weaning weight (CW) by 6 yr after first calving, were estimated using records of 1,886 Hereford cows from a selection experiment with three selected lines and a control line. Weaning weights were adjusted to 200 d of age and for sex and age of dam. Estimates of heritability and genetic and environmental correlations were obtained by restricted maximum likelihood with bivariate animal models, with year of birth of 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 LPL|O ranged from 0.05 (0.01) to 0.15 (0.03). Estimates of genetic correlations (SE) among LPL|O ranged from 0.74 (0.14) to 1.00 (0.00), and estimates of environmental correlations ranged from 0.67 (0.05) to 0.98 (0.01). Estimates of heritability (SE) for NB, NW, and CW were 0.17 (0.05), 0.21 (0.06), and 0.18 (0.01). Estimates of genetic correlations (SE) among NB, NW, and CW ranged from 0.96 (0.02) to 0.99 (0.01). Estimates of environmental correlations (SE) ranged from 0.93 (0.01) to 0.99 (0.01). Estimates of genetic correlations for L6 with NB, NW, and CW were near 1.00 (0.09). Estimates of environmental correlations (SE) ranged from 0.57 (0.03) to 0.60 (0.03). Estimates of genetic change per year (SE) for L6 were low for all lines and ranged from –3.53 (2.09) to 4.63 (2.11) d/yr. Genetic trends for NB and NW were negligible for all lines. Genetic trends for CW were low and ranged from –2.81 (1.67) to 3.29 (1.76) kg/yr. Differences in genetic trends between selected lines and control were not significant (P > 0.05). Estimates of environmental trends (SE) over all lines were –104.00 (25.48) d/yr, –0.26 (0.02) calves/yr, –0.25 (0.02) calves/yr, and –55.10 (15.63) kg/yr, for L6, NB, NW, and CW, respectively. Selection for LPL|O or LP could be successful in a breeding program, but may be relatively slow due to the low magnitude of heritability and extended generation interval.

Key Words: Beef Cattle • Longevity • Selection

This article has been cited by other articles:

				M. H. Van Melis, J. P. Eler, H. N. Oliveira, G. J. M. Rosa, J. A. V. Silva II, J. B. S. Ferraz, and E. Pereira Study of stayability in Nellore cows using a threshold model J Anim Sci, July 1, 2007; 85(7): 1780 - 1786. [Abstract] [Full Text] [PDF]