Abstract
This study investigated the effect of supplementing the diet of calves with two direct fed microbials (DFMs) (Saccharomyces cerevisiae boulardii CNCM I-1079 (SCB) and Lactobacillus acidophilus BT1386 (LA)), and an antibiotic growth promoter (ATB). Thirty-two dairy calves were fed a control diet (CTL) supplemented with SCB or LA or ATB for 96 days. On day 33 (pre-weaning, n = 16) and day 96 (post-weaning, n = 16), digesta from the rumen, ileum, and colon, and mucosa from the ileum and colon were collected. The bacterial diversity and composition of the gastrointestinal tract (GIT) of pre- and post-weaned calves were characterized by sequencing the V3-V4 region of the bacterial 16S rRNA gene. The DFMs had significant impact on bacteria community structure with most changes associated with treatment occurring in the pre-weaning period and mostly in the ileum but less impact on bacteria diversity. Both SCB and LA significantly reduced the potential pathogenic bacteria genera, Streptococcus and Tyzzerella_4 (FDR ≤ 8.49E-06) and increased the beneficial bacteria, Fibrobacter (FDR ≤ 5.55E-04) compared to control. Other potential beneficial bacteria, including Rumminococcaceae UCG 005, Roseburia and Olsenella, were only increased (FDR ≤ 1.30E-02) by SCB treatment compared to control. Furthermore, the pathogenic bacterium, Peptoclostridium, was reduced (FDR = 1.58E-02) by SCB only while LA reduced (FDR = 1.74E-05) Ruminococcus_2. Functional prediction analysis suggested that both DFMs impacted (p < 0.05) pathways such as cell cycle, bile secretion, proteasome, cAMP signaling pathway, thyroid hormone synthesis pathway and dopaminergic synapse pathway. Compared to the DFMs, ATB had similar impact on bacterial diversity in all GIT sites but greater impact on the bacterial composition of the ileum. Overall, this study provides an insight on the bacteria genera impacted by DFMs and the potential mechanisms by which DFMs affect the GIT microbiota and may therefore facilitate development of DFMs as alternatives to ATB use in dairy calf management.
Highlights
The microbiota composition of the gastrointestinal tract (GIT) influences the health outcome of animals as well as their productivity[1,2]
A total of 8,824,437 sequences of the 16S rRNA genes were generated from amplicon sequencing of 159 samples representing rumen (RuD), ileum (IlD) and colon (CoD) digesta and ileum (IlM) and colon (CoM) mucosa of 16 calves on day 33 and another 16 on day 96 for a total of 4 calves per treatment (Control (CTL), Saccharomyces cerevisiae boulardii CNCM I-1079 (SCB), Lactobacillus acidophilus BT1386 (LA), and an antibiotic growth promoter (ATB))
It is well documented that the bacterial community diversity pattern and composition differ across GIT sites[31,32]
Summary
The microbiota composition of the gastrointestinal tract (GIT) influences the health outcome of animals as well as their productivity[1,2]. Diet and the weaning process affect the development of the GIT and microbial colonization in calves during the early period of growth[8,9]. Microbial colonization and subsequent fermentation processes in the rumen during the early period of growth was influenced by feeding (natural or artificial) practice[13]. Our hypothesis was that supplementation of calf ’s diet with SCB and LA will increase the colonisation and establishment of beneficial bacteria in the different GIT sites. The present study investigated the effect of feeding SCB and LA on the colonisation and development of the GIT microbiota, their effects on the composition of bacterial populations in different GIT sites and their potential mechanisms of action during the early period of calf ’s growth
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