ERP113246 PRJEB30767 ena-STUDY-IBERS-12-01-2019-04:34:06:279-58 ena-STUDY-IBERS-12-01-2019-04:34:06:279-58 Effects of dietary dehydrated lucerne or cardoon meal on the modulation of ruminal biohydrogenation and microbial community in lambs Lucerne (Medicago sativa) is a forage legume widely used as a protein source in ruminant rations whereas cardoon meal is a novel by-product from oil extraction of cardoon seeds (Cynara cardunculus var. altilis) and is rich in protein, unsaturated fatty acids (FA) and polyphenols. The effect of substituting dehydrated lucerne with cardoon meal was examined on the ruminal fermentation, biohydrogenation of FA (RBH) and the rumen microbial community of lambs fed a concentrate diet containing either 15% dehydrated lucerne (CON, n = 8) or cardoon meal (CMD, n = 7) for 75 days pre-slaughter. In comparison to CON, lambs fed CMD had lower dietary intakes (P < 0.05) of C18:3 n-3 (-26.7%) but greater intakes of C18:0 (+34.7%), C18:1 n-9 (+20.2%), C18:2 n-6 (+19.6%) and polyphenols (+117.1%). Dietary treatment did not influence ruminal fermentation characteristics and the absolute abundance of rumen bacteria, methanogens, fungi or protozoa. Feeding CMD promoted RBH resulting in a greater concentration (P < 0.05) of ruminal C18:0 (+71.7%) and total saturated FA (+41.3%) and lower C18:1 n-9 (-21.8%) and monounsaturated FA (-46.0%) compared to CON-fed lambs. In addition, the inhibition of RBH in CON-fed lambs resulted in a higher concentration of trans-10 C18:1, trans-11 C18:1, total odd- and branched-chain FA and total trans-18:1 isomers in the ruminal digesta. Dietary effect on RBH was accompanied by changes in the rumen bacterial community with lower population diversity indices observed in lambs fed CMD compared to CON. Lambs fed CMD displayed a greater relative abundance of Proteobacteria and a lower abundance of Bacteroidetes and Fibrobacteres compared to CON-fed lambs. At the genus level, CMD mediated a specific shift from Prevotella, Alloprevotella, Solobacterium and Fibrobacter to Ruminobacter, suggesting that these bacterial genera may play an important role in RBH. Canonical correspondence analysis indicated that the rumen bacterial community in CON-fed lambs was positively correlated with cis-16 C18:1, trans-10 C18:1 and C18:3 n-3. Overall, results demonstrated that dietary replacement of dehydrated lucerne with cardoon meal promoted RBH through a modulation of the bacterial community, which may consequently reduce the accumulation of health-promoting unsaturated FA in ruminant meat or milk. Lucerne (Medicago sativa) is a forage legume widely used as a protein source in ruminant rations whereas cardoon meal is a novel by-product from oil extraction of cardoon seeds (Cynara cardunculus var. altilis) and is rich in protein, unsaturated fatty acids (FA) and polyphenols. The effect of substituting dehydrated lucerne with cardoon meal was examined on the ruminal fermentation, biohydrogenation of FA (RBH) and the rumen microbial community of lambs fed a concentrate diet containing either 15% dehydrated lucerne (CON, n = 8) or cardoon meal (CMD, n = 7) for 75 days pre-slaughter. In comparison to CON, lambs fed CMD had lower dietary intakes (P < 0.05) of C18:3 n-3 (-26.7%) but greater intakes of C18:0 (+34.7%), C18:1 n-9 (+20.2%), C18:2 n-6 (+19.6%) and polyphenols (+117.1%). Dietary treatment did not influence ruminal fermentation characteristics and the absolute abundance of rumen bacteria, methanogens, fungi or protozoa. Feeding CMD promoted RBH resulting in a greater concentration (P < 0.05) of ruminal C18:0 (+71.7%) and total saturated FA (+41.3%) and lower C18:1 n-9 (-21.8%) and monounsaturated FA (-46.0%) compared to CON-fed lambs. In addition, the inhibition of RBH in CON-fed lambs resulted in a higher concentration of trans-10 C18:1, trans-11 C18:1, total odd- and branched-chain FA and total trans-18:1 isomers in the ruminal digesta. Dietary effect on RBH was accompanied by changes in the rumen bacterial community with lower population diversity indices observed in lambs fed CMD compared to CON. Lambs fed CMD displayed a greater relative abundance of Proteobacteria and a lower abundance of Bacteroidetes and Fibrobacteres compared to CON-fed lambs. At the genus level, CMD mediated a specific shift from Prevotella, Alloprevotella, Solobacterium and Fibrobacter to Ruminobacter, suggesting that these bacterial genera may play an important role in RBH. Canonical correspondence analysis indicated that the rumen bacterial community in CON-fed lambs was positively correlated with cis-16 C18:1, trans-10 C18:1 and C18:3 n-3. Overall, results demonstrated that dietary replacement of dehydrated lucerne with cardoon meal promoted RBH through a modulation of the bacterial community, which may consequently reduce the accumulation of health-promoting unsaturated FA in ruminant meat or milk. ENA-FIRST-PUBLIC 2019-03-11 ENA-LAST-UPDATE 2019-01-12