The genetic foundation of fitness and reproduction traits in Australian pig populations. 1. Genetic parameters for weaning to conception interval, farrowing interval, and stayability

Abstract

Data from 2 large Australian piggeries were used to estimate genetic parameters and to examine fixed effects for weaning to conception interval (WCI) and farrowing interval (FI) measured in the first 3 reproductive cycles, and sow stayability from the first to later i parities (STAY1i,). WCI and FI recorded following the first farrowing had low heritabilities (h2 = 0.08-0. l0), but estimates did not significantly differ from zero when these traits were recorded in later parities. Heritability estimates for STAY increased with parity of recording, ranging from 0.05 for STAY12 to 0.06 (STAYl3) and 0.09 (STAYl4). Genetic correlations between WCI12 or PI12 and stayability traits ranged from -0.22 to -0.54. Selecting for short WCI following the first farrowing should have favourable consequences for longevity of sows. Important fixed effects for WCI and FI were lactation length and the number of piglets nursed. Both short (<20 days) and long (>29 days) lactation periods led to an increase in WCI12 relative to the optimum lactation length of 21-23 days. WCI also increased with the number of piglets nursed by 1 day/additional piglet for litters ranging in size from <7 to >10 piglets. STAY was little affected by correcting for the average number of piglets born in previous litters.