Females had the rectal temperature measured just
before receiving the first insemination. A state of
hyperthermia was considered when body temperature
was 39.4 or above (Muirhead and Alexander, 1997). As only
one gilt and one sow had the rectal temperature of 39.4 and
39.5 8C, respectively, this factor could not be included as a
potential risk factor of a return to estrus, due to insufficient
heterogeneity.