The mobilization of fatty acids during food deprivation is a selective process studied in different species (humans, rodents, birds, viverrids). The aim of this work was to study the effect of fasting on selective mobilization in commercial pigs. A total of 16 barrows (Large White×Landrace (167 kg±12.5 kg live weight) were subdivided into two homogeneous groups, one subjected to 12 h and the other to 60 h of fasting (fasting time) before slaughtering. For each pig inner and outer backfat layer were sampled at slaughter and at ham trimming 24 h later (sampling time). Increasing the fasting time and the sampling time after slaughter caused an increase in the amount of free fatty acids in both layers. Therefore it can be argued that during fasting lipolysis is stimulated and remains active also after slaughtering. The factors that stimulate lipolysis determine a greater mobilization of unsaturated fatty acids than saturated ones. Thus fasting time may influence the suitability of pork for processing and conservation, since free fatty acids are more suitable for oxidation than the esterified ones.

The objective of this work was to investigate the expression of heat shock protein 70 (HSP70) by Western blot (WB) in swine liver. Subsequently, the study aimed to apply this method to two experimental groups of heavy pigs raised in different confinement systems: intensive/indoor (Group A) and extensive/outdoor (Group B). Thirty-six crossbred commercial heavy pigs were divided as follows: Group A (eight castrated males and eight females) was equally distributed into two single-sex indoor pens (1.02 m2/pig); Group B (11 castrated males and nine females) was kept in one single (partially grassy and partially wooded) open area of about 6000 m2. Group A was slaughtered at 41 weeks of age (170 ± 9 kg) and Group B at 48 weeks of age (172 ± 13 kg). At the abattoir the livers of all the animals were collected and analyzed by WB assay in order to quantify the levels of HSP70. Moreover, a further liver sample was taken from the same animals in order to investigate the cellular localization of HSP70 by immunohistochemistry (IHC). The interaction between sex and group resulted statistically significant (P = 0.001). When stratified by sex, Group A showed significantly higher HSP70 values compared with Group B for both male and female subjects (P < 0.001). Stratifying by group, males showed significantly higher HSP70 values than females in Group A (P < 0.001), whereas no statistical differences were observed between sexes for Group B (P = 0.653). The IHC results evidenced cytoplasmic immunoreactivity in a granular pattern in both groups. The different expression pattern observed by WB could prove to be a useful tool in the assessment of pig health and welfare.