THE GENETIC FOUNDATION OF FITNESS AND REPRODUCTION TRAITS IN AUSTRALIAN PIG-POPULATIONS .1. GENETIC-PARAMETERS FOR WEANING TO CONCEPTION INTERVAL, FARROWING INTERVAL, AND STAYABILITY
E. Tholen et al., THE GENETIC FOUNDATION OF FITNESS AND REPRODUCTION TRAITS IN AUSTRALIAN PIG-POPULATIONS .1. GENETIC-PARAMETERS FOR WEANING TO CONCEPTION INTERVAL, FARROWING INTERVAL, AND STAYABILITY, Australian Journal of Agricultural Research, 47(8), 1996, pp. 1261-1274
Data from 2 large Australian piggeries were used to estimate genetic p
arameters and to examine fixed effects for weaning to conception inter
val (WCI) and farrowing interval (FI) measured in the first 3 reproduc
tive cycles, and sow stayability from the first to later i parities (S
TAY(1i)). WCI and FI recorded following the first farrowing had low he
ritabilities (h(2) = 0.08-0.10), but estimates did not significantly d
iffer from zero when these traits were recorded in later parities. Her
itability estimates for STAY increased with parity of recording, rangi
ng from 0.05 for STAY(12) to 0.06 (STAY(13)) and 0.09 (STAY(14)). Gene
tic correlations between WCI12 or FI12 and stayability traits ranged f
rom -0.22 to -0.54. Selecting for short WCI following the first farrow
ing should have favourable consequences for longevity of sows. Importa
nt fixed effects for WCI and FI were lactation length and the number o
f 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 nu
rsed by 1 day/additional piglet for litters ranging in size from <7 to
>10 piglets. STAY was little affected by correcting for the average n
umber of piglets born in previous litters.