Growth parameters, behavior, and meat and ham quality of heavy pigs subjected to photoperiods of different duration

To attain a good level of animal welfare, pigs require a sufficient nvironmental illumination. Therefore, minimum levels for light duration and light intensity have been set up by the European legislation (Directive 2008/120). An experimental trial was designed to determine whether an increased duration of the photophase (up to 16 h of light per day) could modify the behavior, productive parameters, and meat and ham quality of Italian heavy pigs. Forty crossbred (Large White × Landrace) castrated males pigs (26 kg initial average BW) intended for Protected Designation of Origin (according to European Union Regulation - European Union, 2012) dry-cured ham production were raised according to Parma ham production rules up to the weight of 160 kg. Pigs were homogeneously allotted to 2 experimental groups, each comprising 20 pigs. The short photoperiod (SP) group received the minimum mandatory number of hours of light per day (corresponding to 8 h/d), whereas the long photoperiod (LP) group was subjected to 16 h of light per day during the whole production cycle. Light intensity was maintained at 40 lux (i.e., the minimum mandatory level) for both the experimental groups. Growth and slaughtering parameters, carcass traits, fatty acid composition, meat and dry-cured ham quality, and animal behavior were assessed. Pigs in the LP group showed a greater live weight and carcass weight compared to the SP group (P = 0.005 and P = 0.007, respectively). Similarly, hams obtained from the LP group were significantly heavier and their weight losses during the dry-curing period were reduced (P < 0.01) when compared to the SP group. No significant differences were detected between the experimental groups as concerns meat and ham quality or fatty acid composition of the subcutaneous fat. Pigs in the LP group spent more time resting and less time pseudo-rooting (P < 0.01). Our results indicate that, given an appropriate dark period for animal rest, an increased duration of the photoperiod, even at the lower mandatory light intensity level, can favorably affect growth parameters of heavy pigs without any negative effect on animal behavior, carcass traits, or meat or long-cured ham quality. Therefore, rearing pigs in semidarkness should be considered as a baseless practice, contrary to animal welfare.