Linseed Oil Supplementation of Lambs' Diet in Early Life Leads to Persistent Changes in Rumen Microbiome Structure

Abstract

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. 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 receiving standard lamb meal, a group receiving lamb meal supplemented with 40 g kg^-1 DM of linseed oil and a group receiving the supplement pre-weaning and standard lamb meal post-weaning. The supplement had no effect on average daily feed intake or average daily weight gain of lambs. Bacterial and archaeal community composition was significantly (p = 0.033 and 0.005, respectively) different in lambs fed linseed oil throughout the study compared to lambs on the control diet. Succinivibrionaceae, succinate producers, and Veillonellaceae, propionate producers, were in a higher relative abundance in the lambs fed linseed oil while Ruminococcaceae, a family linked with high CH₄ emitters, were in a higher relative abundance in the control group. The relative abundance of Methanobrevibacter was reduced in the lambs receiving linseed compared to those that didn't. In contrast, the relative abundance of Methanosphaera was significantly higher in the animals receiving the supplement compared to animals receiving no supplement (40.82 and 26.67%, respectively). Furthermore, lambs fed linseed oil only in the pre-weaning period 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. Again, Succinivibrionaceae and Veillonellaceae were in a higher relative abundance in the group fed linseed oil pre-weaning while Ruminococcaceae were in a higher relative abundance in the control group. This study shows that lambs fed the dietary supplement short-term had a rumen microbiome that remained altered even after supplementation had ceased.

Keywords: dietary intervention; early life; linseed oil; rumen microbiome.

FIGURE 1

Relative abundance of (A) bacterial and (B) archaeal genera in the rumen of lambs fed standard lamb meal (Control group), lambs fed linseed oil for 16 weeks (L group) and lambs fed linseed oil pre-weaning only (L-P group).

FIGURE 2

Non-metric multidimensional scaling (nMDS) plot of rumen (A) bacterial community structures and (B) archaeal community structures at genus level. Control lambs (C) are represented by the aaa symbol, lambs fed linseed oil for 16 weeks (L) are represented by the bbb symbol and lambs fed linseed oil pre-weaning only (L-P) are represented by the aaadown symbol.

FIGURE 3

Concentration of volatile fatty acids (VFAs) measured after 16 weeks in the rumen of lambs on the control diet (C), lambs fed linseed oil for 16 weeks (L) and lambs fed linseed oil pre-weaning only (L-P)- (A) propionic acid, (B) butyric acid, (C) acetic acid, (D) ratio of acetic plus butyric acid to propionic acid.

FIGURE 4

Heat maps showing correlations between the relative abundance of sequences assigned to each bacterial genus and VFA concentrations (acetic, butyric and propionic) in the rumen of lambs fed the control diet (C), lambs fed linseed oil pre-weaning only (L-P) and lambs fed linseed oil for 16 weeks (L). Pearson’s correlation coefficients (r) are given, with r < 0 indicating a negative correlation (red), r = 0 indicating no correlation (white) and r > 0 indicating a positive correlation (green).