Piglet performance and physiological effects linked to reduced glucosinolate transformations in feed products based on rapeseed pressed cakes

The nutritional quality of rapeseed press cakes (RPCs) in piglet feed is closely linked to its digestibility and the content of glucosinolates. This study investigates the significance of intact glucosinolate (glc) levels and degree of glc transformations on piglets performance. Four different RPCs were made from a low glc (11 µmol/g seed DM) containing B. napus L. seed variety Lioness (RPC‐LW, RPC‐LXW, RPC‐LC, RPC‐LCD). RPC made from the variety Excalibur containing the upper level of glc (24 µmol/g seed DM) of double rapeseed and produced at higher and prolonged temperature (RPC‐UXW) served as negative control, while soya bean protein concentrate served as positive control. Piglets (8 kg) were fed ad libitum diets balanced for RPC protein content, with RPC inclusion of 84–98 g/kg (day 0–14) and 151–178 g/kg (day 15–50). Glc transformation was reduced from 42% to 24% (7.3–4.2 µmol/g RPC) when the temperature input was lowered in the warm pressing of oil, while the glc loss was less pronounced (17%) when cold pressing was applied. The following feed pelleting process further reduced Glc concentration from 11% to 40% in warm‐pressed RPCs and 54 to 85% in cold‐pressed RPCs. The RPC products replaced soya bean protein without any negative effects on performance, except for piglets served cold‐pressed RPC, which had a reduction in average daily weight gain (ADG) (5%–7%, p < 0.05, Day 15–50). RPC in the feed led to increased liver weight in all piglets (p = 0.026). This may point at long‐term effects from feeding with RPC. Intestinal absorption of intact glcs was proven by their detection in urine. In conclusion, warm‐pressed RPC can be used as feed for piglet, while the presence of active myrosinase may have a negative effect on performance and cakes should either be included in lower amounts than used in the present study (18%) or include myrosinase inactivation before use.