THE NUTRITIVE-VALUE FOR RUMINANTS OF LUPIN SEEDS FROM DETERMINATE PLANTS AND THEIR REPLACEMENT OF SOYA BEAN MEAL IN DIETS FOR YOUNG GROWINGCATTLE

Lupin seeds produced from two new varieties (CH304/70, CH304/73) of UK -grown autumn-sown determinate genotypes were studied for their chemic al composition including fatty and amino acid contents together with t he rumen degradation of nitrogen and the post-ruminal availability of undegraded nitrogen. A soya bean meal (SBM) was included in the rumen degradation work for comparison. In addition, for one variety (CH304/7 0), digestibility and energy values were measured using sheep and a co mparison with SBM as a protein supplement for young growing bulls was made. The crude protein contents of varieties CH304/70 and 73 were 362 and 305 g kg(-1) dry matter (DM), respectively, and their chemical co mposition was in general similar to previous reports. Rumen degradabil ity of nitrogen (at assumed rumen outflow rate of 0.05 h(-1)) was high er than that of SBM (650, 610 and 550 g kg(-1) feed nitrogen for CH304 /70, CH304/73 and SBM, respectively) but considerably lower than most other reports largely because of much lower nitrogen solubilities. Thi s was possibly due to the relatively coarse milling used in the presen t work Increasing the proportion of CH304/70 in the diets of wether sh eep from zero to 0.4 produced Linear responses in the digestibility of all fractions except lipid, and led to an estimated metabolisable ene rgy value for the lupin seeds alone of 16.9 MJ kg(-1) DM. When SBM in the diets of growing bulls (liveweight similar to 180 kg) was replaced on an isonitrogenous basis by lupin seeds no significant effect on pe rformance was seen. Crown Copyright (C) 1997 Published by Elsevier Sci ence B.V.