Skip to main content
ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #106067
Title: CHARACTERISTICS OF LINE 1 HEREFORD FEMALES RESULTING FROM SELECTION BY INDEPENDENT CULLING LEVELS FOR BELOW AVERAGE BIRTH WEIGHT AND HIGH YEARLINGWEIGHT OR BY MASS SELECTION FOR HIGH YEARLING WEIGHT

Author
item Macneil, Michael
item URICK, J - RETIRED USDA-ARS
item DECOUDU, G - MONTANA STATE UNIVERSITY

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2000
Publication Date: 9/1/2000
Citation: MACNEIL, M.D., URICK, J.J., DECOUDU, G. CHARACTERISTICS OF LINE 1 HEREFORD FEMALES RESULTING FROM SELECTION BY INDEPENDENT CULLING LEVELS FOR BELOW AVERAGE BIRTH WEIGHT AND HIGH YEARLINGWEIGHT OR BY MASS SELECTION FOR HIGH YEARLING WEIGHT. JOURNAL OF ANIMAL SCIENCE. 2000. v. 77. p. 2345-2351.

Interpretive Summary: Consequences of selection depend on a large number of interacting effects within the production system. The cow herd consumes approximately two-thirds to three-fourths of the feed energy used in beef production systems. In this research, changes in characteristics of mature beef cows resulting from two selection protocols based on juvenile growth were evaluated. Selection for below average birth weight and high yearling weight simultaneously is a selection strategy that has popular appeal for beef producers. While this strategy can result in improved post-natal performance relative to random selection, growth performance is compromised somewhat with the resulting cattle becoming earlier maturing and smaller at all ages than under selection for high yearling weight alone. The popular appeal of selecting for low birth weight and high yearling weight stems from the perception that this strategy should result in improved calving ease while maintaining an increasing genetic trend in growth. Based on the results of this research this perception is apparently flawed.

Technical Abstract: Simultaneous selection for low birth weight and high yearling weight has been advocated to improve efficiency of beef production. Two sublines of Line 1 Hereford cattle were established by selection either for below average birth weight and high yearling weight (YB) or for high yearling weight alone (YW). The objective of this study was to estimate genetic trends for traits of the cows. A three parameter growth curve [W = A(1 - B*exp(-K*age))] was fitted to age (d)-weight (W) data for cows surviving past 4.5 years of age (n = 738). Resulting parameter estimates were analyzed simultaneously with birth weight and yearling weight. To estimate maternal additive effects on gain from birth to weaning (MILK) the two-trait model previously used to analyze birth weight and yearling weight was transformed to the equivalent three-trait model with birth weight, gain from birth to weaning, and gain from weaning to yearling as dependent variables. Heritability estimates were: 0.32, 0.27, 0.10, and 0.20 for A, B, K, and MILK,. Genetic correlations with direct effects on birth weight were: 0.34, -0.11, and 0.55 and with direct effects on yearling weight were: .65, -0.17, and 0.11 for A, B, and K, respectively. Genetic trends for YB and YW respectively were: A (kg/generation), 8.0 +_ .2 and 10.1 +_ .2; B (x1000), -1.34 +_ .07 and -1.16 +_ .07; K (x1000), -14.3 +_ .1 and 4.3 +_ .1; and MILK (kg), 1.25 +_ .05 and 1.89 +_ .05. Beef cows resulting from simultaneous selection for below average birth weight and increased yearling weight had different growth curves and reduced genetic trend in maternal gain from birth to weaning relative to cows resulting from selection for increased yearling weight.