Chemical and acidic composition of Longissimus dorsi muscle of Comisana lambs fed with Trifolium subterraneum and Lolium multiflorum

Aim of this study was to evaluate the effects of grazing on Trifolium subterraneum and Loliummultiflorum, as pure or associated crops, on the chemical composition and on the fatty acidprofile of the intramuscular lipids of the meat of lambs. Forty Comisana male lambs, onaverage weighing 13.75±1.90 kg, were divided into four homogenous groups of ten andcalled, in relation to the diet: group T those grazing on T. subterraneum; Group L on L. multiflorum;Group TL on adjacent monocultures of T. subterraneum and L. multiflorum (66.6 and33.3% of surface, respectively); Group LT on adjacent monocultures of T. subterraneum andL. multiflorum (33.3 and 66.6% of surface, respectively). Every 10 days, samples of foragespecies ingested by grazing lambs were collected and analysed. At 90 days of age, with anaverage live weight of 25.44, 23.44, 24.69 and 24.75 kg for T, L, TL and LT group, respectively,all lambs were slaughtered and a sample of Longissimus dorsi muscle for each animal wascollected to study the chemical and acidic composition. No significant differences amongthe groups were observed for the growth performance and for the chemical composition ofthe meat. As regards the fatty acid classes, significant differences (P < 0.05) were observedfor the monounsaturated fatty acids, which were lower in the group T (35.46%) than those ofthe groups L (38.24%), TL (38.63%) and LT (38.59%), whereas, significant higher values for thegroup T were observed for the polyunsaturated fatty acids of the n-3 (4.49%) and n-6 (8.26%)series than those of the n-6 series for group L (6.79%; P < 0.05) and than those of both seriesfor group LT (n-3 = 3.64%; P < 0.05 and n-6 = 6.43%; P < 0.05). The fatty acids that have significantlydetermined the modifications of the acidic classes were: oleic acid, which showedsignificant (P < 0.05) lower values in the group T (26.70%) than the levels observed in thegroups L (30.33%), TL (30.39%) and LT (30.63%) and the linoleic, linolenic and rumenic acidswhich were significantly (P < 0.05) higher in the groups T (linoleic = 5.13%; linolenic = 1.97%;rumenic = 0.46%) and TL (linoleic = 4.75%; linolenic = 1.82%; rumenic = 0.41%) than those ofthe groups L (linoleic = 4.10%; linolenic = 1.52%; rumenic = 0.26%) and LT (linoleic = 3.95%;linolenic = 1.42%; rumenic = 0.33%). These differences could be due to the different dynamicactivity of the cellulolytic bacteria in the rumen, related to the different levels of fibrous fractions of the diets. No significant difference was observed for saturated fatty acid, unsaturated/saturated fatty acids ratio and Atherogenic and Thrombogenic indices among thegroups, whereas, PUFA/SFA ratio showed significant (P < 0.05) higher value in group T thanthat in the group LT.T. subterraneum monoculture grazed as monoculture (T) and in mixture with L. multiflorum(66/33, TL) increased the linoleic, linolenic and rumenic acids improving the dieteticnutritionalcharacteristics of the lamb meat.