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Three experiments compared the nutritive value of whole unprocessed seeds of lupins ( Lupinus angustifolius cultivar ‘Uniharvest’), cowpeas ( Vigna unguiculata cultivar ‘Caloona’) and navy beans ( Phaseolus vulgaris cultivar ‘Actolac’) as supplements for young sheep fed low quality roughage ad libitum. In Experiment 1, a 49 day feeding trial, three levels (10, 20 and 40 g kg −1 W 0.75 ) of lupin supplement progressively increased total dry matter (DM) intake, liveweight (LW) gain and wool growth, but roughage intake was decreased by 19% and 48% when 20 and 40 g kg −1 W 0.75 respectively were fed. When cowpea supplement was fed, responses as feed intake and LW gain were similar to those observed for lupin supplement. Wool growth was increased by 10 and 20 g kg −1 W 0.75 cowpeas, but was not further increased by 40 g kg −1 W 0.75 . A low level (10 g kg −1 W 0.75 ) of navy bean supplement resulted in similar intake and productivity responses to those observed with the same level of lupins or cowpeas. However, when higher levels (20 and 40 g kg −1 W 0.75 ) of navy beans were offered, although total intake increased, LW gain and feed conversion efficiency (FCE) were lower than for equivalent levels of lupins or cowpeas. Also sheep offered 40 g kg −1 W 0.75 of navy bean consumed only 82% of the supplement, and wool growth was lower than for the equivalent level of lupins. Addition of a mixture of terramycin and flavomycin antibiotics to the lupin supplement fed at 40 g kg −1 W 0.75 increased LW gain, but did not affect FCE or wool growth. Antibiotic addition to navy beans had no effect on performance. In Experiment 2 20 g kg −1 W 0.75 of each of the legume seeds was fed as a supplement for roughage. Total intake and organic matter digestibility were similar for the three supplements and greater than when no supplement was fed. However, the concentration of nitrogen in faeces was higher when cowpea or navy bean rather than lupin supplement was fed. In Experiment 3 when rumen cannulated sheep were supplemented with each of the legume seeds, DM, lectin activity and trypsin inhibitor activity rapidly disappeared from synthetic fibre bags containing ground legume seeds and incubated in the rumen, suggesting rapid and extensive fermentation or solubilization of these components. It was concluded that lupin and cowpea supplements resulted in similar intake and growth responses in these young sheep fed low quality roughage. However, reduced wool growth when a high level (40 g kg −1 W 0.75 ) of cowpeas was fed suggested that protease inhibitors in this grain legume reduced amino acid availability to the sheep. A low level (10 g kg −1 W 0.75 ) of navy bean was satisfactory as a supplement, but when moderate or high levels (20 or 40 g kg −1 W 0.75 ) were used LW gain and wool growth were lower than expected, presumably due to detrimental effects of antinutritional factors in the navy beans which were not inactivated by rumen fermentation. |
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