Genetic gain and economic weights in selection for boar fertility traits in a cross-breeding system

Abstract Text:

Four boar fertility traits: semen volume (VOL, ml), semen concentration (CON, x10³/mm³), progressive motion of spermatozoa (MOT, %), and abnormal spermatozoa (ABN, %) provide complementary information about boar fertility. It is now feasible to include these traits in genetic improvement programs. However, there is limited information on the genetic and economic parameters necessary to assess the impact of selection for these traits. Objectives of this study were to estimate economic weights for these traits and to evaluate genetic gain that results from including them in a three-tier, three-way crossbreeding scheme (maternal nucleus lines A and B and paternal nucleus line C). Three cases were simulated in ZPLAN. Case I (baseline case) encompassed genetic selection for number of pigs born alive (NBA), litter birth weight (LBW), adjusted 21-day litter weight (A21), number at 21 days (N21), days to 113.5 kg (D113), backfat (BF), average daily gain (ADG), feed efficiency (FE), and lean carcass % (LEAN). Case II included Case I and a novel fertility indicator called DOSES that combines the four boar fertility traits (VOL * CON / 1000) * (MOT / 100 * (1-(ABN / 100)) / (number of spermatozoa per dose). Case III included Case I and the four boar fertility traits individually. Estimated economic weights represent the net economic gain per unit of genetic improvement in VOL, CON, MOT, ABN, and DOSES ranged from 0.21 to 1.44 $/ml, 0.12 to 0.83 $/ x10³/mm³, 0.61 to 12.66 $/%, -0.53 to -10.88 $/%, and 2.01 to 41.43 %/dose as number of semen collections per week was reduced from 7 to 1. Average genetic gains remained stable for the maternal traits (NBA, LBW, A21, N21) in Case II and III, relative to Case I. Genetic gains in Cases II and III relative to Case I dropped by 59.2% and 25.8% (BF), 50% and 50% (FE), and 84.4% and 59.4% (LEAN), respectively. The relative economic weights decreased in Case II and III relative to I by 21% and a 15% (line A), 18% and 12% (line B) and 32% and 23% (line C), respectively. Selection including the four boar fertility traits separately (Case III) was preferable to using one combined indicator (Case II) by enabling genetic gains in these traits without compromising the genetic gains in the maternal traits.

Keywords: boar fertility traits, economic weights, three-way crossbreeding scheme