Production and behavioural traits of heavy pigs subjected to two illumination periods

According to latest EFSA’s recommendations (2007) on the welfare of fattening pigs, the aim of the present trial was to give a contribution to the still debated problem concerning pig requirements in terms of environmental illumination. Forty hybrid pigs (26 kg BW) were homogeneously allocated into two experimental groups (20 animals per group) each containing four replications of five pigs: group LL (Long Lighting) in which pigs were exposed to a 16-hour/day light period and group SL (Short Lighting) in which, in compliance with minimum legislative standard, pigs were subjected to a 8-hour/day light period. For both groups the light intensity was 40 lux, equivalent to the minimum mandatory level. Pigs were fed on the basis of their metabolicBW up to a maximum of 3.3 kg/pig/day. From 100 to 160 kg BW pigs were monthly videotaped over a 24-hour period in order to assess, by scan sampling, their behaviour. Growth parameters and post-mortem outcomes were submitted to analysis of variance (GLM procedure) with lighting duration as the main effect.For non-parametric data (behavioural traits), Mann-Whitney test (NPAR1WAY procedure) was used. During the first phase of the experiment (0-118 days of trial), animals receiving the longer illumination period (LL group) showed a significant (P<0.01)improvement of average daily weight gain and a reduction (P<0.05) of feed conversion rate, leading to a higher (P<0.05) final body weight. At slaughtering, despite similar lean meat yields (assessed by F-o-M), pigs on LL group produced heavier carcasses and heavier hams (P<0.01). With respect to behavioural traits, pigs receiving the longer illumination period were more calm as demonstrated by a higher percent of lying behavior and by a lower incidence of pseudo-rooting behavior (P<0.01). From a general standpoint it can be concluded that a prolonged photoperiod with a low light intensity could have some positive effects both on production and behavioural traits of pigs.