To attain a good level of animal welfare, pigs require a sufficient environmental illumination and therefore, minimum standards for light duration and light intensity have been set up by the European legislation (Directive 2008/120), according to E. Nannoni and colleagues at the University of Bologna in Italy.

They conducted an experiment, published in Journal of Animal Science, that was designed to determine whether an increased duration of the photophase (up to 16 hours of light per day) would affect the behaviour, productive parameters, and meat and ham quality of Italian heavy pigs.

They used 40 crossbred (Large White × Landrace) castrated males pigs (initial weight 26kg) intended for Protected Designation of Origin (according to European Union Regulation 1151/2012, European Union, 2012) dry-cured ham production were raised according to Parma ham production rules up to the weight of 160kg.

Pigs were allocated to two experimental groups, each comprising 20 pigs. The short photoperiod (SP) group received the minimum mandatory number of hours of light per day (corresponding to eight hours per day), whereas the long photoperiod (LP) group was subjected 16 hours of light per day during the whole production cycle.

Light intensity for both groups was maintained at 40 lux, i.e. the minimum mandatory level.

Growth and slaughter parameters, carcass traits, fatty acid composition, meat and dry-cured ham quality and animal behaviour were assessed.

Pigs in the LP group had heavier live and carcass weights than the SP group (P=0.005 and P=0.007, respectively).

Similarly, hams obtained from the LP group were significantly heavier and 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 in terms of meat or 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).

The researchers stressed that both groups had an appropriate dark period for the animals to rest.

They concluded that the increased photoperiod, even at the lower mandatory light intensity level, favourably affected growth parameters of heavy pigs, without any adverse effects on animal behaviour, carcass traits or meat or long-cured ham quality.

Rearing pigs in semi-darkness should be considered an unnecessary practice that is contrary to good animal welfare, Nannoni and colleagues concluded.

Reference

Martelli G., E. Nannoni 1, M. Grandi, A. Bonaldo, G. Zaghini, M. Vitali, G. Biagi and L. Sardi. 2015. Growth parameters, behavior, and meat and ham quality of heavy pigs subjected to photoperiods of different duration. Journal of Animal Science. 93:758-766.

March 2015