Objective 1: Evaluate the mechanism of action and functional effects of short chain fatty acid (SCFA) preparations as diet supplements on gut cell-microbial interactions in broilers. Sub-objective 1.1:Compare the effects of SCFA-supplementation on growth parameters in healthy and Eimeria-infected broiler chickens. Sub-objective 1.2 Determine the role of short-term and long-term SCFA diet supplementation on microbiome composition and metabolite profiles in modern production, fast-growing broilers (FGB) and slow-growing (SGB), physiologically robust heritage varieties infected with Eimeria species. Sub-objective 1.3:Evaluate the potential for SCFA supplementation to modulate the expression of genes and proteins associated with nutrient uptake in healthy and Eimeria-infected SGB and FGB lineages. Objective 2: Assess low level gut inflammation as a model for compromised growth and nutrient efficiency, and determine the potential for selective feeding of natural anti-inflammatory constituents to replace antibiotics for growth promotion. Sub-objective 2.1: Establish the capacity of gut inflammation and treatment with traditional antimicrobial growth promoters (AGP) to alter weight gain, feed conversion ratios, and changes in microbiome composition and metabolite profiles in broilers. Sub-objective 2.2:Develop and implement strategies to decrease the effects of bacterial toxins on the gut through the inclusion of novel milk- or plant-derived compounds or fats and oils in the diet. Objective 3: Assess, develop, and apply microbiome- and metagenomic-based strategies in poultry to define the role of the microflora in the regulation of nutrient uptake and utilization in the gastrointestinal tract during post-hatch development of broilers. Sub-objective 3.1: Establish which microbial population distribution patterns are likely to associate with SGB versus FGB production phenotypes in poultry. Sub-objective 3.2: Determine the capacity for diet supplementation with plant-derived gamma (')-and delta (d)-tocopherol-enriched mixed tocopherol oils (predominantly non-alpha-tocopherol isoforms) to modify the antioxidant environment of different segments of the gut in regard to modulating the microbiome of the broiler for improved gut integrity.
This project’s focus is to minimize challenges to gut health that compromise growth by constraining absorption of dietary nutrients and/or and redirecting nutrient use from growth to supporting immune function and tissue repair. Understanding the host-microflora interactions that influence gut health is critical for developing strategies to increase the efficient use of ingested nutrients by broilers for meat production in the absence of antimicrobials. Objective is specific to the topic of alternatives to antimicrobials to maintain efficient growth in broiler chickens through the use of novel formulations of short chain fatty acids, essentially nutritional prebiotics, to offset deficits in growth arising from gut parasitic infection with coccidia. Objective 2 addresses one of the purported mechanisms of actions through which antimicrobial growth promoters improve feed efficiency in poultry, namely, modulating gut inflammation. The intent here is to develop nonantimicrobial, non-drug approaches such as isoforms of vitamin E other than the traditional alpha tocopherol to mitigate gut inflammation thus sparing nutrients for growth that otherwise would be used to fight the inflammation or simply be lost through a lack of intestinal absorption. Objective 3 addresses the role of the gut microflora in optimizing the efficiency of nutrient processing in the gut towards better protein deposition. A unique opportunity will be available through the direct comparison of gut microbiome populations derived from modern fast growing broilers versus those obtained from more slow-growing heritage breeds and varieties. In addition the project will be the first to assess directly the impact of the oxidation-reduction environment in the gut on population changes in the microflora.
For Objective 1.1., a study was carried out to determine the effects of addition of butyrate or valerate (short chain fatty acids) on performance of broilers infected with Eimeria maxima, a common gastrointestinal pathogen. Performance data from infected chickens indicated that addition of 0.25% butyrate to the diet can result in decreased feed conversion ratio (FCR) and increased body weight gain at 7 days post infection (PI). However, at ten days PI there were no differences between infected birds on normal diet or diet containing butyrate. A second study was carried out to determine the effect of valerate on the performance of E. maxima infected birds, however no effect of the SCFA was noted. Lastly a third study was performed on the effects of butyrate on E. acervulina infected birds, and no effect was found in birds consuming the medicated diet. An analysis of the microbiome from E. maxima infected birds consuming butyrate was carried out, which concluded that E. maxima had an effect on the microbiome but the butyrate did not. For Objective 2.2., a study was conducted to determine if colostrum (derived from cattle) would serve as an alternative to traditional antimicrobial products. An in-depth metabolite profile of the ileal digesta collected from chickens fed a low level of a purified bovine colostrum for 5 days resulted in a metabolite profile significantly enhanced in its basic anti-inflammatory capabilities. Feed efficiency was improved 9% and the presence of tyrosine-nitrated proteins, gut epithelial nitrooxidative stress biomarkers, significantly decreased compared to control non-supplemented birds. The improvement in anti-inflammatory capacity of the digesta from colostrum-fed birds was evident in an improved balance in omega-3 versus omega-6 fatty acids, decreased glutathione precursor and metabolites, and an increased oligosaccharide content. The data suggest that low-level, short-term use of bovine colostrum could be beneficial in stabilizing the gut of chickens post-hatch and assist in the efficient uptake of nutrients for growth by providing an environment of compounds with known associations with reducing cell inflammatory processes. For Objective 3.1., an experiment was conducted using six different meat chicken lines/breeds, of which three were slow-growing and three were fast-growing lines to determine whether microbial population distribution patterns are likely to be associated with the phenotypes of those broiler chickens. In a floor-pen setting, all six lines were fed the same diet and were grown until they reached five weeks of age. Every week weight and feed intake of chickens were recorded. Samples of gastrointestinal tract, as well as the content, were collect for gene expression and metagenome analysis. The birds were characterized by different trajectory pattern of growth, with fast-growing broilers having the highest body weight while slow-growing birds were characterized by slower growth rate in comparison to fast growing lines. Similar patterns were observed for feed intake. The fast-growing broilers were also characterized by lower feed conversion ratio. Currently, gastrointestinal tract samples are being analyzed for microbiome. For Objective 3.2., two experiments were designed and conducted to determine the effects of supplementing broiler diets with pure alpha-tocopherol or each of three levels of mixed isoform tocopherol oil (enriched with gamma- and delta tocopherols) on the response to infection with the gut parasite E. maxima. The first trial focused on the recovery phase of the infection largely quantifying the effects of the various tocopherols on the post-infection compensatory gain and feed efficiency (days ten through 14 PI). The second experiment focused on the time surrounding the onset (day 4 PI) and peak (day 7 PI) of the infection to evaluate the mechanism of action of the various tocopherol treatments to mitigate inflammation. Currently, samples and data collected from these two experiments are being analyzed. Additionally, a study was carried out to determine whether access to feed immediately post-hatch will affect microbiome development, gastrointestinal tract permeability and immune system development, as well as calcium and phosphorus transporter gene expression. Immediately after hatch broiler chicks had access to feed or were subjected to 48 h feed delay to mimic industry settings. Delayed access to feed up to 72 h is a normal practice in poultry industry due to uneven hatching, sorting, vaccination and transportation to the farms. The results suggest that delayed access to feed affects body weight and feed intake (growth efficiency), microbiome development, and gene expression level of proteins involved in tight junction that are responsible for gut permeability, as well as the gastrointestinal tract immune system development. This could also suggest that broilers subjected to delay in feed access are more susceptible to infection or have delayed response to infection.
1. Delayed access to feed post-hatch affects the gastrointestinal microbiome, permeability and immune system response development. The gastrointestinal tract (gut) plays a key role in the digestion and absorption of nutrients, but also forms a physical barrier and first line of defense between the host and the gut environment. A functional gut barrier is essential for optimal health and efficient production in poultry; therefore, in the current broiler system, chicks are deprived of food and water up for to 72 hours post-hatch due to uneven hatching, hatchery procedures and transportation time to farms and post-hatch feed delay results in lower body and organ weight, higher feed conversion ratio and mortality, and delayed post-hatch growth and gut development. ARS researchers at Beltsville, Maryland, determined that delayed access to feed immediately post-hatch affects the gene expression level of proteins that are involved in the formation of regions in the gut (tight junctions) responsible for the select transport of nutrients across the gut barrier. Properly functioning tight junctions prevent transport of microorganisms, toxins and/or harmful metabolites into the blood stream. These results indicate that development of the gastrointestinal tract, as well as overall health and production efficiency, of broiler chickens could be easily improved by shortening the delayed access to feed period in hatchery. These results provide new avenues of research and tool for industry where the overall health and production efficiency of broilers could be easily improved by shortening the time before placement on the farm.
Elsasser, T.H., Miska, K.B., Kahl, S., Fetterer, R.H., Martinez, A. 2018. Temporal pattern changes in duodenal protein tyrosine nitration events in response to Eimeria acervulina infection in chickens. Infection and Immunity. https://doi.org:10.1093/jas/sky140.
Miska, K.B., Fetterer, R.H. 2017. The mRNA expression of amino acid and sugar transporters, aminopeptidase, as well as the di- and tri-peptide transporter PepT1 in the intestines of Eimeria infected broiler chickens. Poultry Science. 1;96(2):465-473. https://doi.org/10.3382/ps/pew303.
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