Skip to main content
ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #146374
Title: GENETIC TRENDS RESULTING FROM SELECTION BASED ON AN INDEX OF BIRTH WEIGHT AND YEARLING WEIGHT

Author
item Macneil, Michael

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2003
Publication Date: 6/1/2003
Citation: MACNEIL, M.D. GENETIC TRENDS RESULTING FROM SELECTION BASED ON AN INDEX OF BIRTH WEIGHT AND YEARLING WEIGHT. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT ABSTRACT #343. 2003. V. 81(SUPPL. 1). P. 86.

Interpretive Summary:

Technical Abstract: The CGC population is a stabilized composite of 1/2 Red Angus, 1/4 Charolais, and 1/4 Tarentaise germplasm. The objectives of this research were to estimate genetic parameters for weight traits of CGC and to evaluate genetic responses resulting from selection based on the index: I = 365-d weight minus 3.2(birth weight). In 1989, a randomly selected control line and a line selected for greater values of the index were established. Average generation intervals were 3.16 +/- 0.04 yr and 3.90 +/- 0.08 yr in the index and control lines, respectively. Over three generations, the index selection line (n = 950) accumulated approximately 212 kg more selection differential than the control line (n = 912). Derivative-free multiple-trait REML methods were used to estimate (co)variance components and to predict breeding values upon convergence of estimates of (co)variance components. Heritability estimates for direct effects were: 0.32 +/- 0.04, 0.49 +/- 0.05, 0.49 +/- 0.05, 0.30 +/- 0.04, and 0.70 +/- 0.04 for the index, birth weight, 365-d weight, 200-d weight, and cow weight, respectively. Heritability estimates for maternal effects were: 0.05 +/- 0.02, 0.11 +/- 0.03, 0.04 +/- 0.02, and 0.19 +/- 0.04 for the index, birth weight, 365-d weight, and 200-d weight, respectively. In the control line, direct genetic changes for the index and its components were small. For the index selection line, direct genetic changes for the index, birth weight, 365-d weight, 200-d weight, and cow weight were 6.0 +/- 0.3, 0.45 +/- 0.09, 7.74 +/- 0.55, 3.42 +/- 0.25, and 6.3 +/- 0.9 kg/generation, respectively. Maternal genetic changes were generally small for both the control and index selection lines. Thus, selection for the index produced positive correlated responses for direct genetic effects on body weight traits at all ages with only minor effects on maternal genetic effects. Results demonstrate that despite a genetic antagonism that compromises selection response for reduced birth weight and increased postnatal growth, favorable genetic responses can be achieved.