Low-glucosinolate rapeseed products for pigs — A review

Abstract

This review embraces work on the use of low-glucosinolate rapeseed meal (LG-RSM) for pigs, mainly published since 1977. Areas discussed are nutritive value, palatability, LG-RSM in starter and growing-finishing diets, effects of different supplements or treatments on the value of RSM, anatomical and physiological effects, meat quality and reproduction when feeding with LG-RSM. Finally, work on fullfat or partially defatted LG rapeseed (RS) is reviewed. The nutritive value of RSM varies between experiments owing to different cultivars, processing techniques and methods of determination. The average value found for crude protein digestibility in LG-RSM was 79% and most values of metabolizable energy (ME) content were in the range 10.5–12.5 MJ/kg DM. Palatability is a limiting factor in starter diets and when growing-finishing pigs are fed ad libitum, but not with a restricted feeding regime at practical levels of LG-RSM inclusion. It seems possible to replace at least half of the supplementary protein with LG-RSM in cereal-based diets for growing-finishing pigs without impairing performance, provided that the lower ME content of RSM is balanced. In starter diets part of the protein supply may be given as LG-RSM (∼ 5% of the air-dry diet). Information on sows is less extensive than on growing animals, but seems to justify the inclusion of up to at least 10% of LG-RSM in the ration. Treatment of RSM with chemicals such as propionic acid, ammonia and formaldehyde, generally impaired nutritive value or palatability of RSM. The thyroid gland and liver of pigs given LG-RSM are enlarged, but to a smaller extent than with older types of RSM. However, recent reports suggest that the thyroid function may be impaired despite a limited enlargement. Reported values of ME content in fullfat LG-RS vary between 17 and 20 MJ/kg DM. Limited amounts (< 10% of the diet) of fullfat or partially defatted LG-RS can be used without impairing performance, but meat quality (taste, structure and fatty acid profile) will be adversely influenced even at lower levels of RS inclusion.