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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 #209216
Title: Effects of competition on expected response to selection for ADG

Author
item CHEN, CHING - UNIV OF NEBRASKA-LINCOLN
item JOHNSON, RODGER - UNIV OF NEBRASKA-LINCOLN
item KACHMAN, STEPHEN - UNIV OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/12/2007
Publication Date: 6/20/2007
Citation: Chen, C.Y., Johnson, R.K., Kachman, S.D., Van Vleck, L.D. 2007. Effects of competition on expected response to selection for ADG [abstract]. Journal of Animal Science. 85 (Supplement 1):134. (Abstract #44)

Interpretive Summary:

Technical Abstract: The objective was to investigate the importance of competition effects on expected response to selection for average daily gain (ADG, g) of boars. A total of 9,720 records from dam lines (1 and 2) and sire lines (3 and 4) were available with 15 boars per pen. Gains (ADG) were measured from about 71 to 161 d of age and weight from 31 to 120 kg. Four models for EBV were compared; each included initial age on test as a covariate and fixed effect of contemporary group (farm-year-season). Direct genetic (d) and competition genetic (c) effects were included in models as random effects. Pen (pn) was included in some models as fixed and in other models as random factors. Models were: Model 1 (d, c, pn random) as full model, Model 2 (d and c), Model 3 (d and pn random), and Model 4 (d, pn fixed). Estimates of direct heritability with Model 1 obtained with MTDFREML for ADG were 0.31, 0.39, 0.21, and 0.26 for lines 1-4. Estimates of heritability of competition effects were near zero. Model 2 produced slightly larger estimates of competition variances (P<0.05 for lines 1-3). Expected responses to selection were calculated under the assumption that estimates of parameters from Model 1 were unbiased. For response of one genetic SD for both components (d and c), the proportions of expected total gain due to competition effects (with economic weights 1 and pen size-1=14) were 53, 19, 62, and 58% for the 4 lines. Average total breeding values (TEBV=EBV(d)+14EBV(c)) for the top 10% of boars selected with Model 1 were 83, 110, 42, and 102 g for lines 1 to 4, respectively. For rankings based on Model 3, but EBV calculated with Model 1, average total breeding values for the top 10% were 76, 110, 18, and 95 g and for rankings based on Model 4 were 66, 108, 12, and 87 g. Further study of correlated responses with models including competition effects seems warranted.