Effect of Spirulina supplementation on plasma metabolites in crossbred and purebred Australian Merino lambs

The effect of supplementing purebred and crossbred Merino lambs with Arthrospira platensis (Spirulina) on plasma metabolite concentrations under pasture-based management system and the influences of sire breed and sex were investigated. A completely randomized experimental design balanced by 4 sire breeds (Merino, White Suffolk, Dorset and Black Suffolk), 3 Spirulina supplementation levels (0, 100 and 200 ml representing the control, low and high, respectively) and 2 sexes (ewe and wether lambs) was utilised. All lambs had ad libitum access to the basal diet of ryegrass pastures and barley. Lambs in the treatment groups were individually drenched daily with Spirulina prior to being released with the control group of lambs for grazing over a 6-week period following a 3-week adjustment phase. At the start and completion of the feeding trial, blood samples were centrifuged and plasma metabolites measured. Data were analysed with Spirulina supplementation level, sire breed, sex and their second-order interactions fitted as fixed effects and metabolite concentrations as dependent variables. Gamma-glutamyl transferase (GGT) concentrations decreased (from 79.40 to 69.25 UI) and glucose increased (from 3.81 to 4.19 mmol/L) as the level of Spirulina supplementation increased from 0 ml in the control to 200 ml in the high treatment groups (P < 0.05). Lambs supplemented at low Spirulina levels had the highest creatinine concentrations (61.75 μmol/L). Interactions between sex and supplementation level significantly affected glucose, aspartate aminotransferase (AST) and Mg concentrations (P < 0.05), while sire breed and supplementation level interactions influenced albumin to globulin (A/G) ratio, creatinine and GGT concentrations. It was demonstrated that Spirulina supplementation does not negatively impact lamb health and productivity.