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Economic gain associated with genomic selection for health in a terminal sire line in pigs
Commercial application of genomic selection (GS) for health depends on economic gains possible relative to costs. The objective of this study was to determine improvements in the overall breeding goal (ΔH) and discounted net returns (ΔΩ) from incorporating genomic selection for health in a terminal sire line breeding program in pigs. A sire line with 40 boars and 1000 sows was simulated deterministically using ZPLAN+ software. Each dam produced 8 piglets/litter (4 males, 4 females) and 20 piglets/year. Selected males and females started breeding at one year of age and continued for 1 and 2 years, respectively. Selected males (40) were mated to 50,000 crossbred females (Large White x Landrace) to produce commercial piglets. Days to market weight (DAYS) and backfat thickness (BF) (heritabilities of 0.4 and 0.5 and economic weights of -$1.77 and -$1.70 per genetic SD, respectively) were recorded on all animals in the nucleus. A health trait (HEALTH) was defined with a genetic SD of 1.0 (heritability = 0.05) and an economic weight that was half of (case A) or equal to (case B) that of DAYS. Three scenarios were considered for trait correlations. Absolute values of all phenotypic and genetic correlations were 0.3 and 0.2, respectively. All genetic and phenotypic correlations were positive except between DAYS and BF for Scenario-I and, between DAYS and the other two traits for Scenario-III. The planning horizon was 10 years (discount rate = 0.05). Fixed and variable costs at the nucleus were $50 and $300 per animal, with additional costs of $100 for genotyping and $10 for recording HEALTH.
Inclusion of genomic predictions for HEALTH in selection indexes for sires and dams increased ΔH per year and ΔΩ over the planning horizon when accuracy of genomic prediction (rMG-HEALTH) was increased, mainly due to greater genetic gain in HEALTH. Scenario-III (with favorable correlations) with case B showed the highest genetic and economic gains. At rMG-HEALTH of 0.8, ΔH and ΔΩ for Scenario-III (case B) were $101.33/year and $510.83/sow in the nucleus, compared to $86.11/year and $396.93/sow without GS. However, the highest extra responses at rMG-HEALTH of 0.8 were under Scenario-I (case B), with increases of 28.9% for ΔH and 135.5% for ΔΩ, partly because of low responses without GS. These responses indicate the potential of implementing GS for health in commercial scenarios. Funding was provided by Genome Canada.
Keywords: genomic selection, health, swine breeding