Linseed oil supplementation of lambs’ diet in early life leads to persistent changes in rumen microbiome structure. Rumen microbiome of lambs

Rumen microbiome structure has been shown to influence animal productivity, feed conversion efficiency, methane emissions and health. Diet has been shown to have a significant impact on microbial community composition in the rumen and could potentially be used to manipulate rumen microbiome structure to achieve specific outcomes. However, the mature rumen microbiome is highly resilient and stable and often dietary interventions only achieve inconsistent or short-lived outcomes. There is some evidence that a window may exist in early life, while the microbiome is being established, where manipulation through diet could lead to long-lasting results. The aim of this study was to test the hypothesis that dietary supplementation in early life will have an effect on rumen microbial composition that will persist even once supplementation is ceased. Twenty-seven new-born lambs were allocated to one of three dietary treatments; a control group received standard lamb meal throughout the study, a second group received lamb meal supplemented with 40 g kg-1 DM of linseed oil throughout the study (~14 weeks) and a third group received the supplement pre-weaning only (4 weeks) and standard lamb meal post weaning. The supplement had no effect on average daily feed intake or average daily weight gain of lambs. At 16 weeks rumen content samples were collected and microbial composition and volatile fatty acid concentrations were analysed and compared between treatment groups. Bacterial and archaeal community composition was significantly (p = 0.033 and p = 0.005 respectively) different in lambs fed linseed oil throughout the study compared to lambs on the control diet. Furthermore, lambs fed linseed oil pre-weaning only had a bacterial community composition significantly (p = 0.015) different to that of the control group, though archaeal diversity and community structure did not differ. This study shows that lambs fed the dietary supplement short-term had a rumen microbiome that remained altered even after supplementation had ceased.