Evidence-Based Prebiotic and Probiotic Solutions For Improving Gut Health and Feed Efficiency in Cattle

Background

Improving gut health and feed efficiency in cattle are priorities for the Canadian beef industry. While industry traditionally achieved this through feeding antimicrobials, increased regulations mean alternatives need to be explored to reap the same benefits to health and production. Prebiotics (nutrients that promote beneficial gut bacteria), probiotics (live microorganisms that provide the host with health benefits), and synbiotics (combining prebiotics and probiotics) are promising strategies. However, adoption of prebiotics, probiotics, and synbiotics by the Canadian beef industry has been slow due to concerns of their reliability, required doses not falling in line with the production cycle and success stories being largely anecdotal and variable. To fill the gap, Dr. Abbot and his team sought to determine if prebiotics, probiotics, and synbiotics can be an effective and reliable alternative to in-feed antibiotics.   

Objectives

• Isolate and characterize rumen bacteria that metabolize yeast mannan 
• Analyze prebiotic-probiotic interactions in an artificial rumen  
• Analyze prebiotic-probiotic interactions in an artificial intestine 
• Determine the effects of synbiotics on feed digestibility in ruminants 
• Determine the effects of synbiotics on production in ruminants  

What They DID

Bovine rumen and fecal samples were collected and were processed to identify the yeast consuming bacteria and categorized by their ability to metabolize yeast which would indicate a positive response to probiotic supplementation. Strains of bovine-adapted Bacteroides thetaiotamicron were isolated that displayed one of two different growth phenotypes: “Medium Growers” (MD33_MG) and “High Growers” (MD40_HG). These bacteria were whole genome sequenced and their genes characterized for how they consumed yeast in the rumen.  

Probiotic and/or prebiotic supplementation was observed using an artificial rumen system. Over a period of 48 hours, production of VFAs, ammonia, and gas were measured to determine the impact on rumen fermentation. The team also used FLA-PS which uses genus-specific fluorescent probes to visually observe the prebiotic-microbe interactions with bacteria of interest.  Artificial intestinal systems were used in a similar fashion, using duodenal and colon samples collected from slaughtered cattle at a local abattoir.  

Finally, 12 cannulated beef cows were used to evaluate the effect of prebiotics on feed digestibility. Silage from the prebiotic diets was used to determine in situ dry matter and neutral detergent fibre disappearance. FLA-PS incubations, production of VFAs and ammonia, and metagenomics were also conducted to be consistent with the artificial systems.  

What They Learned

Two distinct growth phenotypes were observed among the yeast degrading bacterial isolates. Isolates were classified as medium growers (MG) or high growers (HG). The different growth phenotypes were a result of transport efficiency – the ability of the bacteria to transport products of digestion into the host’s cells which was determined to be caused by differences in transport proteins present in MG and HG phenotypes. FLA-PS incubations supported this observation, as the high grower (MD40_HG) showed faster and higher accumulation than the medium grower. This finding has far reaching implications for responses of probiotic bacteria to feed polysaccharides. 

Prebiotics only needed to be supplemented at 1% of the diet to show increased microbial richness in the artificial rumen. However, prebiotic treatment decreased microbial fermentation efficiency. Systems supplemented with prebiotics had a lower production of gas, VFAs, and ammonia. Probiotic treatments had less of an impact on microbial richness and reduced microbial fermentation. Synbiotic treatments showed the differences in how probiotic bacteria will utilize supplementation from noticeable variable metabolites in their carbohydrate profiles. Furthermore, alternative prebiotics (i.e., inulin) and probiotics (i.e., Bifidobacterium boum) were also studied using this experimental system. Inulin alone was found to have more of an impact than the probiotic or synbiotic treatment. 

These treatments had limited effects on feed digestibility in the canulated cattle. Total degradation of dry matter significantly increased over 20 days but was the only variable to do so. These prebiotics altered the structure and diversity of the rumen microbial communities, while microbial richness and evenness was decreased. At the genus level, prebiotics increased the relative abundance of Lactobacillus species. This study also found that different prebiotics will affect the microbiome differently with inulin  increasing the abundance of Prevotellaceae members, and Bio-Mos increasing the abundance of Bifidobacterium species.  

What It Means

Understanding ways to improve cattle performance is a priority for the resiliency of beef production. Developing an effective prebiotic, probiotic or synbiotic will require an understanding of how they contribute to the health of the animal. Advanced research tools developed in this project in combination with traditional models for studying cattle metabolism and performance, have provided a new platform to study how prebiotics work and which would be most beneficial. Within this project, prebiotics (Bio-Mos®) altered fermentation and microbial communities in different regions of the gastrointestinal tract. Furthermore, prebiotic supplementation did not impede feed digestibility, and altered the microbial community towards a more beneficial state. An important finding is that prebiotics (i.e., inulin, Bio-Mos®) had a more significant effect on digestion than probiotics. In addition, there was much more promise in terms of being able to use prebiotics over probiotics on farm.