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Nonruminant Nutrition Symposium I: A Sustainable Approach of Reducing Antibiotics in Swine Production

Summary by: Anne Kamiya, MS

The 2021 American Society of Animal Science Midwest Virtual Meeting session, Nonruminant Nutrition Symposium I (March 9, 2021), comprised of eight presenters from diverse educational backgrounds. The overarching theme of this seminar was the development of intervention strategies to reduce antibiotic use in postweaning swine. Gut bacteria that inhabit the digestive system have a profound impact on the immune status and metabolism of an animal with profound effects on vitamin production, fermentation of non-digestible substrates and tissue accretion. The ability of sub-therapeutic antibiotics to increase growth rate via multifactorial and unidentified mechanisms involving the gut microbiome and immune system are well known. However, ethical concerns and regulatory changes in response to increasing antibiotic resistance necessitates the search for alternative solutions. Topics focused primarily on impacts of diet on gut microbiota, alterbiotics, low protein diets and the use of alternative or supplemental amino acid sources.

Maxwell Lectureship: Why Resist: Harnessing immune-microbiome interactions for improved swine gut health” presented by Dr. Crystal L. Loving (USDA-ARS-National Animal Disease Center)
The term “alterbiotics” was introduced in this talk, that is to say, alternatives to antibiotics. Alterbiotics are a broad category that includes feed additives such as probiotics, prebiotics, phytochemicals, microbial metabolites like short-chain fatty acids (SCFA), enzymes and more. The exploration into alterbiotics as a replacement for antibiotics could be said to have five goals: to (1) promote growth, (2) modulate immune status, (3) enhance intestinal integrity, (4) modulate microbial composition or function and (5) prevent or limit pathogenic infection. In the discussed study, feeding piglets dietary resistant potato starch (RS) raised fecal butyrate (a SCFA) and lactate and correlated with microbial population changes in the gut in piglets fed RS versus the control group. In order to determine if RS might prevent or limit bacterial infection, nursery pigs were inoculated with Salmonella. Fecal excretion of Salmonella was significantly reduced, meaning there was less of this pathogen to deal with in both the environment and in the animal. The study supported feeding RS as a way to alter fecal microbiota and mitigate infection. However, a deeper understanding of whether RS in conjunction with other alterbiotics can become a viable alternative for sub-therapeutic antibiotics are needed.

“The Role of Crude Protein in Reducing the Need for Antibiotics in the Post-weaning Period” presented by Dr. John Pluske (APRIL)
This talk reviewed several pieces of literature that explored low protein diets as a way to improve the fecal consistency of piglets during the post-weaning period. Low crude protein without antimicrobials reduced diarrhea without affecting performance whereas high crude protein diets were associated with an increased incidence of post-weaning diarrhea. Dietary protein intake is not 100% efficient and a flow of excess nitrogenous compounds undergoes proteolytic fermentation in the colon by nitrogen fermenting gut bacteria into proinflammatory byproducts (e.g., ammonia, amines and branched-chain fatty acids). Nitrogen utilization can therefore be improved by reducing protein intake and adding synthetic and crystalline amino acids to compensate for any losses in essential amino acids (AA). The take home message was that minimizing indigestible protein losses by feeding a low protein diet and supplementing synthetic and crystalline AA can reduce diarrhea and improve fecal quality, but at added cost. However, low protein diets are not a replacement for antibiotics, perhaps necessitating the synergistic use of low protein diets with other antibiotic alternatives.

“The Danish Perspective to Remove Medicinal Zinc and Reducing the Use of Antibiotics in Swine Production” presented by Dr. Hanne Maribo (Pig research Centre DK, SEGES)
Antibiotics and medicinal zinc (ZnO) have historically been used to improve piglet growth and reduce diarrhea in the postweaning period, but both are no longer a viable prophylactic option. Finding replacements without negative effects on animal welfare and productivity is multifactorial and complex. In this talk, the speaker discusses various feed options SEGES has explored to replace medicinal zinc, i.e., reduced protein diets, additives like organic acids, enzymes, probiotics, blood plasma, seaweed and yeast products. Nothing to date equals ZnO, however, low protein diets show promise because they consistently and significantly reduce the incidence of postweaning diarrhea. Unfortunately, productivity is also hindered by low protein diets. A solution to this problem may be in increasing the protein content in feed when pigs reach 30 kg as losses in the postweaning period may be recovered by feeding increased protein in the finisher stage. A very low protein heat-treated “Superdiet” with added benzoic acid, butyric acid, Bactocell, milk products and blood plasma was also evaluated. The Superdiet reduced diarrhea incidence comparable to medicinal zinc but with significant impacts on cost and production. A combination of feed options including low protein diets to replace antimicrobials seems promising but comes with a steep cost and productivity hurdle to overcome.

“Feed Additives That Optimize Nitrogen Bio-availability in Nursery Pigs Fed Reducing Crude Protein Diets” presented by Dr. Tsungcheng Tsai (University of Arkansas)
In this talk, feed additives that might optimize nitrogen (N) bioavailability in nursery pigs fed reduced crude protein diets (RCP) was discussed. The RCP diets have been repeatedly shown to improve the incidence of postweaning diarrhea however low protein during the postweaning period also negatively impacts average daily gain and productivity. Meeting amino acid (AA) requirements with RCP diets is therefore a challenging obstacle to overcome. Feed additives that may increase N absorption such as bioactive peptides and organic acids may be a viable solution to this problem. Bioactive peptides are generally absorbed more easily than free amino acids in the small bowel, suggesting they may have increased bioavailability. They also act as antioxidants with antimicrobial and anti-inflammatory properties. The fish peptide Peptiva was one such peptide brought up in this talk—the study discussed found Peptiva improved growth performance, modulated systemic immune cells and the gut microbiome—however this was in the context of a high Zinc Oxide (ZnO) diet. Whether Peptiva would have the same impact on growth and health in a diet lacking ZnO is yet to be explored. Overall, though RCP diets were very effective in reducing postweaning diarrhea in the absence of antibiotics or ZnO, it is clear that a combination of feed additives will be needed to optimize nutrient absorption and productivity.

“Agriculture Residues as a Possible Sustainable Approach to Replacing Antibiotics in Animal Nutrition” presented by Dr. Ricardo Ekmay (SVP Nutrition & Product Development Arbiom Inc.)
In this talk, alternative protein sources such as insect meal, chlorella, single cell proteins (SCP), yeasts and bacterial meal were discussed. Sustainable alternative feedstuffs would need to be studied thoroughly to make sure they are bioavailable and improve animal health and productivity. SylPro (a SCP yeast product) was discussed as having promise as a protein alternative. Torula yeast was another alternative protein source exhibiting anti-inflammatory properties. There is also bacterial meal –  amino acid bacterial biomass products made of non-pathogenic Escherichia coli or other nonpathogenic organisms like Methylococcus capsulatus. Bacterial meals must be used with caution however as they are known to contain pro-inflammatory compounds. This talk emphasized how alternative protein ingredients may have the potential to impact animal health and production while simultaneously promoting sustainability, but this new area of study remains in dire need of further exploration.

“Raised Without Antibiotics, Lessons Learned” presented by Dr. Whitney Lincoln (DMV, Director of Production Smithfield)
This talk focused on Smithfield Foods’ Raised Without Antibiotics (RWA) program which ran from 2016-2019 in the midwestern United States. Largely discussed was the program’s ability to integrate and achieve their strategies and nutritional plans for healthy antibiotic-free pigs. The goal of this program was not only to raise antibiotic-free pigs but to assure good animal welfare, health management and husbandry, traceability and fiscal responsibility. A prevention/action plan was set up for the program, which focused on health, nutrition, environment and daily care. The program included over 400K pigs and was considered a success. Success was defined by getting above the target of full market value pigs from intake of the program to market. The average daily gain and feed to gain ratio was positive. The program boasted success both financially and in terms of animal welfare and with only 1.53% of animals being removed from the RWA program due to the need for antibiotic treatment.

“A Veterinarian’s Perspective on How Health and Nutrition Intersect” presented by Dr. Sarah D. Hough (DVM, DSM Nutritional Products)
The focus of this talk was on the relationship between animal nutrition and health with an emphasis on a more holistic approach to the role nutrition plays in disease and productivity. Because immunity and nutrition are interrelated, there is a need for Veterinarians and Nutritionists to work together to explore nutritional solutions for health and growth problems that currently lack solutions. For example, the speaker brings up three scenarios where nutritional factors play a key role in disease: (1) a thiamine-responsive neurological disorder of swine with polioencephalomalacia, (2) post-weaning diarrhea is strongly related to how piglets start on feed, and (3) late-term lameness, although multifactorial, can be related to nutrition (vitamin D, calcium, or phosphorous). Other issues discussed in this overview of the literature included the relationship of pelvic organ prolapse to nutritional intake, water quality (biofilms negatively impacting piglet performance), antinutritional compounds, feeding management and precision feeding. The role vitamins and nutrition play in gastrointestinal functionality was also a key point of discussion. Although vitamin deficiency is not normally an issue in pigs, challenges that lead to disrupted redox balance can increase the need for certain nutrients and should be considered. Overall, the points made in this talk were valid, urging a more holistic approach to animal wellbeing and growth.

“When Too Many Feed Additives Is Not a Sustainable Approach to Replacing Feed Antibiotics” presented by Dr. Casey L. Bradley (The Sunswine Group LLC)
The removal of antibiotics and Zinc Oxide (ZnO) from animal feed due to regulatory and environmental concerns has had a profound impact on production systems. Without antibiotics, animal mortality increases and performance decreases. Finding adequate replacements for antibiotics and ZnO that are profitable, sustainable and provide the same function (enhancing growth performance and reducing diarrhea) is a current area of investigation across animal science research in a multitude of fields. The huge variety of potential feed additives that may replace antibiotics are overwhelming in scope, including prebiotics, probiotics, organic acids, bioactive peptides, direct feed microbials, yeasts, vitamins and trace minerals in excess of daily requirements, crystalline amino acids, enzymes, phytogenic products and much more. However, the ability of these products, either alone or in combination with other products, have not demonstrated an effectivity and profitability comparable to antibiotics and ZnO. A series of experiments by the Hanor System (Oklahoma, USA) was reviewed, in which a variety of feed additives were evaluated for their impact on the gut microbiota and productivity. In each study discussed, products that were potentially useful as antibiotic replacements were found but would result in financial losses. The speaker emphasizes that finding solutions to this complex problem may not be a one size fits all approach

The unedited recording of this symposium can be found on the meeting website.