The diets were formed from a basal diet consisting of 660 g barley, 243 g wheatfeed, 34 g extracted rapeseed meal, 38 g whole rapeseed and 25 g mineral–vitamin supplement per kg fresh mass, which the boars had been fed before the experiment. With the exception of additional atocopherol acetate (as an antioxidant), the basal diet was fed alone as an unsupplemented control diet. The tuna oil (30 g kg–1, Tuna Orbital Oil, Scotia Pharmaceuticals Ltd, Carlisle) was added to the basal diet as a supplement. The diets were fed as follows. The unsupplemented boars were fed 2.5 kg daily, consisting of 2.0 kg basal diet and 500 g of a premix obtained by mixing basal diet with 1.5 g a-tocopherol acetate kg–1. Similarly, for the supplemented diet, boars were fed 2.575 kg daily, consisting of 2.0 kg basal diet and 575 g of a premix obtained by mixing basal diet with 150 g tuna