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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 #218863
Title: Effects of Social Interactions on Empirical Responses to Selection for Average Daily Gain of Boars

Author
item CHEN, CHING-YI - UNIV OF NEBRASKA-LINCOLN
item JOHNSON, RODGER - UNIV OF NEBRASKA-LINCOLN
item NEWMAN, SCOTT - GENUS-HENDERSONVILLE, TN
item KACHMAN, STEPHEN - UNIV OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2008
Publication Date: 3/1/2009
Citation: Chen, C., Johnson, R.K., Newman, S., Kachman, S.D., Van Vleck, L.D. 2009. Effects of Social Interactions on Empirical Responses to Selection for Average Daily Gain of Boars. Journal of Animal Science. 87(3):844-849.

Interpretive Summary: Competition among pigs fed together in pens may affect growth rates. If competitive effects have a genetic basis, then estimates of these effects might improve selection responses. Effects of competition on responses to selection for growth rate were examined with records of 9,720 boars from 2 dam lines and 2 sire lines. Pens contained 15 boars. Gains were measured from about 71 to 161 d of age and weight from 31 to 120 kg. Models included fixed effects of contemporary groups and initial test age as a covariate, and random direct genetic, competition genetic, and environmental competition effects. Pen was included in some models as fixed and in other models as random factors. Estimates of direct heritability with the complete model were 0.31, 0.39, 0.21, and 0.26 for the four lines. Estimates of heritability of competition effects were near zero. Predicted responses to selection showed that the proportions of expected total gain due to competition effects were 53, 21, 61, and 58% for the 4 lines. Genetic superiorities of the top 10% of boars were calculated for boars ranked using reduced models, but with breeding values calculated using the complete model. Average total breeding values for the top 10% of boars selected with the complete model were 83, 110, 42, and 102 grams per day for the 4 lines. For rankings based on an alternative model considering pens as random effects, average total breeding values for the top 10% were 76, 110, 18, and 94 grams per day with correlated responses for genetic competition effects from selection for direct effects of 0, 2, -3, and 3 grams per day for the 4 lines.

Technical Abstract: Effects of competition on responses to selection for ADG were examined with records of 9,720 boars from dam lines (1 and 2) and sire lines (3 and 4) provided by Pig Improvement Company. Each line was analyzed separately. Pens contained 15 boars. Gains (ADG) were measured from about 71 to 161 d of age and weight from 31 to 120 kg. Models included fixed effects of contemporary groups and initial test age as a covariate, and random direct genetic (d), competition genetic (c), and environmental competition (ce) effects. Pen (pn) was included in some models as fixed and in other models as random factors. Estimates of direct heritability with Model 1 (the full model with d, c, pn random) were 0.31, 0.39, 0.21, and 0.26 for lines 1-4. Estimates of heritability of competition effects were near zero. Empirical responses to selection with Model 1 were calculated using the parameter estimates from Model 1. 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 of 1 and pen size-1=14) were 53, 21, 61, and 58% for the 4 lines. Genetic superiorities of the top 10% of boars were calculated for boars ranked using reduced models, but with EBV calculated using the full model (Model 1). Average total breeding values (TEBV=EBVd+14EBVc) for the top 10% of boars selected with Model 1 were 83.40, 110.14, 42.43, and 102.35 g for lines 1 through 4, respectively. For rankings based on Model 3 (d and pn random), but EBV calculated with Model 1, average total breeding values for the top 10% were 75.88, 110.02, 18.25, and 94.48 g with empirical correlated responses for genetic competition effects from selection for direct effects of 0.08, 1.50, -2.64, and 2.72 g for lines 1-4.