Effects of feeding concentrate diets containing narrow-leaf lupin, yellow lupin or soya when compared with a control diet on the productivity of finishing lambs

An experiment investigated the hypothesis that incorporating lupins (Lupinus spp.) into lamb finishing diets would not alter lamb productivity and carcass characteristics when compared with a soya bean (Glycine max) meal concentrate or a commercial concentrate diet. The 4 dietary treatments were: narrow-leaf lupin (cv. Prima), yellow lupin (cv. Wodjil), soya bean meal and a commercial (control) lamb finisher diet. Eighty male Suffolk-cross castrated lambs were used. Diets were formulated so as to be iso-nitrogenous (160 g kg DM-1) and iso-energetic (ME 11.0 MJ kg DM-1). The experiment comprised of 3 phases: a 14-day covariate period, a 14-day adaptation period (14 days prior to day 0) and an 8-week measurement period (Day 0-56). During the covariate period, lambs were kept as one group on pasture. During the adaptation period, lambs were housed and offered increasing amounts of their treatment diets. Each blocking group was allocated at random to a set of four adjacent pens within 4 treatment blocks. During the measurement period, animals were offered straw and concentrate ad libitum, with refusal margins of 0.10 to 0.15 d-1. Lambs were weighed and condition scored every 7-days throughout the experiment. The measurement period was split into two phases. From Day 0-28, live weight data from all lambs was collected to determine liveweight gain, with the mean of each replicate pen of 5 lambs used in the data analysis. The mean liveweight gain of lambs offered concentrates incorporating soya, narrow-leaf lupin, yellow lupin or a commercial control diet were 185, 229, 193 and 166 g d-1, respectively. There was no significant effect (P>0.05) of dietary treatment on the liveweight gain of lambs offered the different dietary treatments. From Day 29 onwards, lambs were selected-out for slaughter and their carcass characteristics determined. The killing out percentage of lambs offered the soya, narrow-leaf lupin, yellow lupin or commercial control concentrate diet was 50.1, 50.7, 51.3 and 50.1%, respectively. Lambs offered a commercial control concentrate or concentrates containing yellow lupin took, on average, 31 days to finish for slaughter, with lambs offered narrow-leaf lupin and soya diets taking 29 and 32 days, respectively.