The return to baseline levels of TT

The return to baseline levels of TT3 and FT3 following a diminished output resulting from LPS challenge occurred later in the TN
group than in the HT group. According to Fliers et al. (1997) and
Boelen et al. (2011), the extent of the decrease in thyroxine during
illness could reflect its severity, which reinforces our hypothesis of
a greater response to LPS in pigs kept at TN. This is supported by
the magnitude of reduction in feed intake during the LPS challenge, which was also higher in the TN compared to HT group. Moreover, the LPS challenge induced a decrease in the gain to feed ratio
in pigs kept at TN, which was not observed in those exposed to HT.
This finding most likely occurs as a consequence of elevated cortisol levels, since this catabolic hormone acts to stimulate adipose
tissue lipolysis and skeletal muscle proteolysis during immunological stress (Johnson, 1997; Webel et al., 1997), so contributing (along
with cytokines) to a redistribution of nutrients from growth to the
immune and inflammatory responses (Spurlock, 1997; Le Floc’h et al.,
2004). Accordingly, the growth of pigs kept at HT was less affected
by the LPS challenge than at TN, suggesting that metabolic disturbances caused by LPS were alleviated by previous heat exposure.