Comparison of raw and roasted narbon beans (Vicia narbonensis) on performance and meat sensory attributes of lambs fed a roughage-based diet

This study examined the effect of raw and roasted narbon bean (Vicia narbon ensis) in a roughage-based diet on growth performance and meat sensory attr ibutes of sheep. Roasting was examined to determine whether it improved pro tein utilisation. Lambs ([Border LeicesterxMerino] x Poll Dorset; 6 months old, mean liveweight of 34.9 kg) were allocated to three treatments (n = 8 per treatment): Nil, lucerne and oaten chaff; raw WNB (chaff plus raw whole narbon bean); and roasted WNB (chaff plus whole narbon bean roasted at 150 degreesC for 45 min). Raw and roasted narbon bean supplied 56% of total pr otein (approximately 15% DM) and were fed for a period of 8 weeks. Growth p erformance was evaluated over 6 weeks followed by a 7 day nitrogen balance measurement in five lambs from each treatment. Remaining three lambs were m aintained on their treatment diets and all lambs were slaughtered at the en d of the nitrogen balance study after blood samples were taken. For Nil, ra w and roasted WNB ADG was 84.3, 158.1 and 171.6 g per day; FCE 16.5, 7.7, 7 .2 kg/kg DM and nitrogen retained 6.4, 6.9, and 8.3 g per day, respectively . At slaughter, HCW, was 18.5, 21.4, 22.3 kg; fat depth 12.6, 17.9, 17.6 mm , and dressing percentage 45.9, 49.9, and 51.4% for Nil, raw and roasted WN B, respectively. There was no significant difference between raw and roaste d WNB for any performance trait. In contrast, all performance traits except for nitrogen retained were significantly (P < 0.05) different between Nil and raw and roasted WNB. Dry matter and organic matter (average 1233 and 11 57 g per day, respectively) intakes were similar across treatments but ther e was a significant (P < 0.05) increase in dry matter (raw, 11.4% and roast ed WNB, 11.9%) and organic matter digestibility (roasted WNB, 10.9%) compar ed with Nil. Changes in metabolite concentrations were variable. However, c hange in PUN concentration at 3 h after feeding was significantly different (P <less than> 0.05) between Nil (1.39 mmol/l) and roasted WNB (0.29 mmol/ l) indicating a reduction in level of rumen-degradable protein in roasted W NB. There were no significant differences in 'aroma liking', 'flavour likin g', 'juiciness', overall acceptability' and 'tenderness' of meat between tr eatments. However, compared with Nil 'aroma strength' and 'flavour strength ' was significantly higher (P < 0.95) in roasted WNB. We conclude that incl usion of raw or roasted narbon brans in a roughage-based dirt improved FCE in young sheep through an increase in ADG and has no detrimental effect on meat sensory properties of lamb. Improvement in performance was achieved th rough an increase in total tract digestibility and hence an increase in ME intake. Roasting narbon beans provided no additional benefit for lamb perfo rmance. (C) 2001 Elsevier Science B.V. All rights reserved.