Comparison of sweet white lupin seed, canola meal and soybean meal as protein supplements for lambs

Abstract

Western-Canadian grown sweet white lupin seed (LS), canola meal (CM) and soybean meal (SM) were compared in situ and in digestibility and feedlot experiments using Romanov × Suffolk lambs. Barley-based (75.5% as fed) diets were isonitrogenous (15.5% crude protein, CP) with LS, CM or SM as protein source. Sunflower hulls were substituted as necessary for protein supplement to ensure the diets were isonitrogenous. The LS used in this trial was relatively low in alkaloids (0.03%), as compared with other lupins, and high in manganese (2347 mg kg−1). In situ, the effective rumen degradability of protein of LS was higher than that of either CM or SM. Rates of DM and protein disappearance were also higher for LS than for CM and SM. Digestibilities of DM organic matter, energy and nitrogen were higher (P < 0.05) in LS than in CM or SM diets, but there were no differences (P > 0.05) among the supplements in digestibilities of starch or NDF. No differences (P > 0.05) were found in feed conversion or DM intake of the three diets. Average daily gain (ADG) of the lambs receiving LS did not differ (P > 0.05) from those of lambs on the other two diets, but lambs on CM had higher ADG (P < 0.05) than lambs on SM. We conclude that LS is comparable to SM and CM as a protein supplement for lambs, provided care is taken to avoid toxic levels of manganese and alkaloids. Key words: Lupin, lamb, protein, canola meal, soybean meal