Growth performance, nutrient digestibility, blood parameters, and carcass characteristics by lambs fed an oregano and...

Shifting ruminal fermentation via feeding a blend of oregano (Organum vulgare L.) essential oils and Co-lactate (EOC; Rum-A-Fresh, Ralco, Inc. Marshall, MN) could improve lamb growth and carcass performance. Eighteen Suffolk × Little Han Tail F1 male lambs (20.3 ± 0.23 kg BW and approximately 3 months old) were randomly assigned using a completely random design to one of three treatments. Treatments were (1) EOC0: basal ration without EOC, (2) EOC4: basal ration plus 4 g/d EOC, and (3) EOC7: basal ration plus 7 g/d EOC. Initial and 24 d BW was similar (P > 0.10), but at 48 and 72 d, lambs fed EOC7 demonstrated greater (P = 0.01) BW compared with EOC0 fed lambs, while lambs fed EOC4 were intermediate and similar (P > 0.05). Average daily gains (ADGs) for 0-24 and 0-72 d were greater (P < 0.05) for lambs fed EOC4 and EOC7 compared with lambs fed EOC0, while DM intake was similar (P > 0.10). Feed conversions for 0-24 d were improved (P < 0.02) for lambs fed EOC4 and EOC7 compared with lambs fed EOC0. However, 0-72-d feed conversions were greater (P < 0.01) for lambs fed EOC7 compared to lambs fed EOC0, with lambs fed EOC4 being intermediate and similar (P > 0.05). DM, NDF, and ADF digestibilities were similar (P > 0.10) among treatments, while CP digestibility was greater (P < 0.01) for lambs fed EOC4 and EOC7 compared with lambs fed EOC0. Carcass weight and dressing percentages were improved (P < 0.01) for lambs fed EOC7 compared with lambs fed EOC0 and EOC4. Head width was greater (P > 0.01) for lambs fed EOC7 compared with lambs fed EOC0 and EOC4, while rump width was greater (P > 0.01) for lambs fed EOC4 and EOC7 compared with lambs fed EOC0. Plasma triglyceride and cholesterol concentrations were lower (P < 0.05) for lambs fed EOC4 and EOC7 compared with lambs fed EOC0, while albumin, total serum protein, and glucose concentrations were greater (P < 0.05) for lambs fed EOC4 and EOC7 compared with lambs fed EOC0. Feeding an EOC blend as an alternative antibiotic growth promoter at 4 and 7 g/d linearly improved lamb growth performance, feed conversions, frame growth, carcass weights, dressing percentages, and immunity.