Effects of rapeseed and rapeseed press cake with different glucosinolate content on the performance of growing pigs

Ground rapeseed (RS) and high fat rapeseed press cake (RPC) were tested in four long-term, ad libitum, feeding experiments with 98 pigs. The RS contained 20 mmol glucosinolates/kg dry matter (DM) and the RPC 19 mmol/kg DM. Diet inclusion of rapeseed products ranged from 0 (control) to 150 g/kg. At the 150g /kg diet level soaked RS and RPC were also tested. (1 1 water/kg, dried at 60 degrees C). Feed intake and live weight gain were decreased by the inclusion of 15 % RS or RPC. The decrease was significant with RS. At inclusion levels of 5 % and 10 % rapeseed was tolerated by pigs and there was no depression in animal performance. However, thyroid weight was increased. Degrading the glucosinolates to <10 % of their initial level by soaking overcame the depression in performance. Based on these results pig diets should contain less than 2 mmol/kg of glucosinolates. This corresponds to 10 % of double zero rapeseed products. Higher proportions of RS or RPC require heat treatment in water. This activates myrosinase in rapeseed and leads to drastic degradation of glucosinolates. Generally, feeding rapeseed products requires supplementary iodine at 250 mu g/kg diet (double the normal requirement).