School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemRoasted legumes for lambs( 1997)Whole lupin (Lupinus angustifolius) and narbon bean (Vicia narbonensis) seeds were dry roasted at 100, 110, 120, 130, 140, 150 and 160C for 15, 30 and 45 minutes. The effect of roasting on in vitro solubility of crude protein (CP) and 'dry matter digestibility (IVDMD) were determined. From the solubility results, seeds roasted at 130C for 15, 30 and 45 minutes were chosen to study the effect of roasting on in situ ruminal disappearance of CP and dry matter (DM). From the in situ results seeds roasted at 130C for 45 minutes were chosen to be fed to crossbred wethers for nine weeks in a 2 (grain legumes) x 2 (raw vs roasted) experiment, in rations consisting of 70% concentrate (legume seed + barley) and 30% roughage (lucerne + oaten chaff). The effect of roasting on feed intake, growth, dry matter and nitrogen digestibility, nitrogen utilization, carcass weight and fat thickness were determined. For both legumes, CP solubility decreased with increasing temperature and time of roasting. The decrease was slightly lower in narbon than in lupin. CP solubility of lupin was decreased from 84.7% (raw) to 17.3% (160C, 45 min) and that of narbon from 68.0% (raw) to 18.3% (160C, 45 min). Dry roasting had no significant (P<0.05) effect on IVDMD measured over 72 hours. In situ DM and CP disappearance was estimated by incubating nylon bags in the rumen of sheep for 2, 6, 12 and 24 hours. Dry roasting significantly (R<0.05) reduced disappearance of CP from the bags with the reduction being slightly greater for lupin (a difference of 17.8% between the raw and 45 min sample after 24 hours of incubation) than narbon (a difference of 15.0% between the raw and 45 min sample after 24 hours of incubation) but had no significant effect on DM disappearance after 24 hours of incubation. Feed intake, growth, feed conversion ratio, dry matter digestibility, carcass weight and fat thickness were not affected (P>0.05) by roasting. Nitrogen retention, expressed as a percentage of nitrogen intake or as a percentage of nitrogen absorbed, was significantly (R<0.05) higher for lambs fed diets containing roasted narbon than for lambs fed diets containing raw narbon (as % of intake 20.3 is 12.3; as % of absorbed 25.6 vs 15.4), but was lower for lambs fed diets containing roasted lupin than those fed diets containing raw lupin (as % of intake 23.1 vs 30.9; as % of absorbed 27.3 vs 37.4). Dry roasting of lupin and narbon bean seeds decreased in vitro CP solubility and reduced ruminai disappearance of CP. Nitrogen utilization in lambs fed diets containing roasted narbon seeds was improved. Roasted lupin significantly (R<0.05) reduced nitrogen utilization in lambs. However, roasting these legumes had no significant (R>0.05) effect on growth.