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Rapeseed pressed cake (RPC) is the co-product from expeller pressing of rapeseed and is a potential protein source for growing pigs. However, despite its high digestibility and constant quality with respect to nutritional value, an excessive heat treatment can decrease protein digestibility and cause non-enzymatic transformation of the intact glucosinolates (glc). It was hypothesized that the optimal RPC quality was achieved by adjusting the temperature during processing in the oil mill and by using double-low B. napus seed with the lowest glc level. Therefore, the objective of the present study was to follow intact glc content and profile from seeds to final feed and to evaluate the RPC product quality on pig performance. For that purpose, a total of four different RPCs were made from a low glc variety (B. napus var. Lioness): (i) RPC-LW, (ii) RPC-LXW, (iii) RPC-LC, (iv) RPC-LCD), differing between them in processing conditions; and a fifth RPC (RPC-UXW) was made from B. napus var. Excalibur, with a higher glc content, serving as negative control. Soybean protein concentrate served as positive control. A total of 3486 piglets (Duroc × Large White × Landrace), with an average BW of 7.0 ± 0.8 kg, were allotted to six treatments (581 piglets/treatment) in a randomised block arrangement. Piglets 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% 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. Feed pelleting process reduced Glc concentration from 11% to 40% in warm-pressed RPCs and 54 to 85% in cold-pressed RPC. The RPC products replaced soybean protein without any negative effects on performance, except for piglets served cold-pressed RPC, which had a reduction in ADG. Dietary RPC led to increased liver weight in all piglets. Intestinal absorption of intact glc was proven by its detection in urine.
In conclusion, warm-pressed RPC could be used in piglet nutrition, tough the presence of active myrosinase might have a negative effect on performance. RPC should either be included in lower amounts or include myrosinase inactivation before use.
Frandsen, H. B., Jensen, S. K., Maribo, H., Markedal, K. E., Schmidt, F., Sørensen, H., Sørensen, S. and Sørensen, J. C. (2019). Piglet performance and physiological effects linked to reduced glucosinolate transformations in feed products based on rapeseed pressed cakes. Journal of Animal Physiology and Animal Nutrition, 103(3), 822-835. https://doi.org/10.1111/jpn.13065
